Archive of Our Own ^beta

Chapter Text

It started as a minor annoyance.
A dull itch, nestled just beneath the plates of his shell, deep enough that even his longest maintenance stylus couldn’t reach it. Donnie chalked it up to phantom nerve firing, maybe some minor post-invasion damage he hadn’t noticed before. He had bigger things to worry about—restoring the tech grid, heighting the security of their lair, tending to Raph's eye and making compression gloves for Mikey's hands, and, of course, keeping Leo from doing anything reckless in his self-imposed redemption arc.

But the itch persisted.

At first it was tolerable. A twitch here, a flex there. But within a few days, it turned unbearable. His shell ached constantly, tingled at the edges, pulsed with a low-grade burning sensation that grew more intense when he moved too fast or hunched over a keyboard too long. His sleep suffered. His appetite dipped. Even Mikey’s homemade chili—spicy enough to scald any Krang—barely registered.

Donnie didn’t tell anyone.

Because how could he? After everything—after the invasion, after Leo nearly died closing the portal, after the city spent months rebuilding and the Hamato Clan put themselves back together one fragile piece at a time—he couldn’t add another worry to the list. Especially not for something as stupid as an itch.

So, he suffered in silence.

“Are you okay?”

Donnie flinched at the sudden voice. He’d been hunched over his workstation for hours, tinkering with a broken cloaking chip, muttering to himself and scratching at the underside of his shell with the edge of a screwdriver.

He looked up. Leo stood at the entrance to the lab, arms folded, brow furrowed. He didn’t have his usual slouch or cocky smirk. Instead, there was that new look he wore sometimes—tight-lipped, sharp-eyed, like he was always bracing for something bad to happen again.

Donnie blinked. “Fine. Why?”

Leo raised a brow. “You’re bleeding.”

Donnie glanced at his hand and realized the screwdriver had dug a small gouge near the seam of his shell. Blood beaded and trickled down his side.

“Oh,” he said flatly. “Didn’t notice.”

Leo strode forward, yanking a clean cloth from Donnie’s med drawer. “That’s the third time this week I’ve seen you do that,” he said, pressing the cloth against the wound. “You’ve been scratching at your shell nonstop.”

Donnie tried to shrug, but the pressure on his shell made him wince. “It’s nothing. Probably dry air. Or allergies. Do turtles even get allergies?”

Leo didn’t laugh. He didn’t even blink. “You’ve been skipping meals. You didn’t even touch the chili last night.”

“I had a deadline—”

“And you’ve barely slept. Mikey said you were up at three in the morning pacing your room.”

Donnie looked away. “So I’m restless.”

Leo’s voice dropped, quieter now. “Don. Please don’t lie to me.”

Donnie swallowed. The itch flared again, crawling like fire under his shell, and he clenched his fists. For a moment, he said nothing.

Then, in a voice smaller than he liked: “It feels like something’s inside me. Burrowed deep. It started as a tickle but now—Leo, it hurts.”

That was all it took.

Leo’s demeanor changed instantly—older twin mode engaged, emergency override. He gently but firmly guided Donnie to sit on the examination bench in the corner of the lab, tugged his purple battle shell off with care, and began scanning with the medical attachment on his arm. His jaw clenched tighter with every pass.

“Leo?”

Leo didn’t answer at first. He tapped through scan results furiously, eyes darting, posture rigid.

Donnie shifted uncomfortably. “Come on. Give me the bad news.”

Leo slowly turned the scanner so Donnie could see. The image showed a thin network of fibrous tendrils embedded near his spinal ridge—organic, glowing faintly with that sickly Krang hue.

Donnie stared. “…That’s not mine.”

“No,” Leo said quietly. “It’s not.”

Fifteen minutes later, Draxum arrived, summoned by Leo through the emergency beacon.

The former villain stepped into the lab with his usual grandiose flourish, but the moment he saw the scans, his expression darkened. “This is residual Krang matter,” he muttered. “Mutated, parasitic… and still active.”

Donnie felt his stomach drop. “Are you saying the Krang are still inside me?”

“Not exactly,” Draxum said, already pulling out surgical tools and reagents from his satchel. “It’s likely leftover biological material from your contact with the Technodrome. A fragment. Dormant—until now.”

Leo’s voice was tense. “Can we remove it?”

Draxum’s eyes flicked to Donnie. “We have to.”

Donnie opened his mouth to make a sarcastic quip, to deflect, to say ‘no big deal’ or ‘well, I always wanted more sci-fi horror in my life’—but the words didn’t come. He just looked at Leo.

And Leo looked back at him like he was already preparing for war.

.

.

.

Donnie stared at the medical scan still projected in front of him, his expression unreadable. The network of invasive, Krang-like tissue pulsed faintly with a sickly pink glow, embedded near the spinal ridge of his shell. No movement, no activity—but alive. Active.

The silence between them stretched long and tight, as if speaking would make it more real.

Finally, Donnie muttered, “Guess that’s why no amount of scratching helped.”

Leo didn’t respond.

Donnie looked over.

His twin stood a few feet away, fists clenched at his sides. His knuckles were pale. His chest rose and fell in a sharp, uneven rhythm, like he couldn’t get a proper breath in. Not like he was angry—no, Leo didn’t have that fire in his eyes. This was something else. Something quieter. Sharper.

“Leo?”

Still nothing.

Donnie sighed, tried to make light of it. “Hey, come on, it’s not like it’s Krang Krang. Just some residual space-goop. Draxum’ll zap it out and we’ll be fine. Right?”

“…Don’t.”

The word came out hoarse. Leo turned to face him, and Donnie saw it clearly now—his eyes were glassy. His voice trembled when he spoke again.

“Don’t pretend this isn’t serious. Don’t act like this isn’t a big deal.”

Donnie blinked, startled. “I’m not—”

“You are.” Leo’s voice cracked. “You always do this. You downplay it. You act like you’re invincible because you’re smart enough to fix everything—but you’re not. You’re not invincible, Donnie.”

Donnie opened his mouth—then closed it again.

Leo stepped forward slowly, as if approaching a glass sculpture about to break. “You’ve been in pain for weeks. You didn’t tell anyone. You could’ve told me. I'm your twin for goodness sakes. We are supposed to tell each other everything”

“I didn’t want to worry you,” Donnie said quietly.

“Well too bad!” Leo barked, the sudden rise in volume shocking both of them. He dragged his hands down his face and turned away, struggling to reel himself back in. “I’m already worried. I’ve been worried since I woke up from my coma and found out that your shell got super messed up from the Technodrome. Gosh Donnie I had to learn from April of all people that you had a seizure. I haven’t stopped worrying.”

The confession lingered in the air, raw and heavy.

Donnie shifted uncomfortably, heart pounding harder. “Leo…”

Leo turned back to him slowly, voice softer now, breaking at the edges. “I can’t lose you. You’re my baby twin, Don. I know we don’t always say it but—you’re part of me. And I need you to be okay.”

Donnie felt something twist deep in his chest.

Leo stepped closer and rested a hand over Donnie’s, where it rested on his knee. His grip was gentle, grounding.

“I’m not mad that something’s wrong,” Leo whispered. “I’m scared. I don’t know what this is or what it’ll do to you, and I can’t protect you from it—not this time.”

For a moment, Donnie didn’t say anything. His throat felt tight, like it had closed up around his next deflection, his next anything.

So instead, he moved his hand—slowly, cautiously—and interlaced his fingers with Leo’s.

“I’m scared too,” he admitted, barely audible. “But I trust you. If anyone’s gonna get this junk out of me… it’s you.”

Leo’s grip tightened. His eyes shimmered, but he nodded, jaw clenched.

“You’re not going through this alone,” he said. “I swear.”

And in the stillness of that moment, with Krang matter glowing behind them and uncertainty ahead, the twins sat side by side—hands linked, hearts pounding, tethered together in fear and in faith.

Chapter Text

Donnie had always believed in logic.
In probabilities. Calculated risk. Methodical efficiency.

He was the scientist. The genius. The one who didn’t panic.
So why was his heart thundering in his ears like a war drum as he lay on the med table, face pressed into the sterile headrest, breath shallow against the cold?

He squeezed his eyes shut as he felt Draxum's gloved fingers trace the center seam of his shell. Leo stood just behind them both, his voice calm, but his energy vibrating with unspoken panic. Mikey and Raph weren’t allowed in the lab for this. Donnie had insisted. He didn't want to see the fear on their faces.

Just Leo. Just Leo was enough.

“Administering localized anesthetic,” Draxum said, voice cool and clinical, but not unkind. “You may feel a sharp pinch, then a numbing sensation across your upper carapace.”

Donnie grunted, resisting the urge to flinch. “Sounds delightful.”

A pause. Then the sharp sting. His limbs twitched.

Leo placed a gentle hand on his shoulder. “You’re okay, Dee.”

Donnie didn’t reply. He just nodded, once.

The scans had shown the Krang matter embedded in a deep layer of the shell, dangerously close to spinal tissue and mystic pressure points. A standard removal wasn’t possible—any reckless slicing could sever nerves, paralyze him, or worse. It had to be done with precision tools, fine surgical lasers, and steady hands.

Draxum had those.

So did Leo.

They worked together in quiet rhythm. Leo’s eyes were locked on the monitor as he guided the micro-scalpel with surgical accuracy. Draxum handled the containment field, isolating the infected tissue with violet energy that shimmered faintly against the lab lights.

Donnie couldn’t see them. But he could feel every vibration, every slight motion. And worse than that—he could feel Leo’s emotions like they were his own.

Tension. Worry. Anger.

Guilt.

It bled off him in waves, through every breath he took and every whisper he muttered under his breath.

“...almost there, Dee. Just a little longer.”

Half an hour in, Donnie’s voice cracked as he muttered, “Y’know, this is easily top three on my ‘Worst Days Ever’ list.”

Draxum didn’t look up. “Humor is often a sign of stress masking emotional fragility.”

Leo gave a soft chuckle. “Or Donnie just can’t shut up, even when he’s sedated.”

“I heard that,” Donnie mumbled.

They worked on.

More glowing strands were extracted and sealed in containment jars—Krang remnants, writhing faintly in the solution. Still alive. Still mutating. Draxum hissed low under his breath.

“This… should not have survived this long. It’s adapting.”

Leo’s brow furrowed. “Adapting how?”

Draxum glanced at the readout. “It’s mimicking Donatello’s cell patterns. Trying to embed itself like it belongs.”

Donnie’s heart skipped a beat. “Okay, now that’s not good.”

“No, it is not,” Draxum said grimly. “Which is why we must remove every trace.”

An hour passed. Then another.

The final strand came loose with a sickening squelch, followed by a tiny hiss of steam. Donnie’s whole body trembled involuntarily as the last of the foreign matter left him.

Leo exhaled like he’d been holding his breath the whole time.

Draxum sealed the final sample, scanning the extraction site. “Clean margins. No further biological anomalies. Recovery prognosis is favorable.”

Donnie’s voice was groggy. “So I’m not gonna mutate into a Krang-freak. Great news.”

Leo knelt beside the bench, leaning in close, one hand still gently resting on Donnie’s arm. His eyes were tired. Shadowed. But soft.

“You did great, Dee.”

Donnie blinked at him. “We did. You were my eyes back there.”

Leo tried to smile, but it faltered.

Donnie noticed. Even sedated, he could see right through him. “Leo?”

Leo hesitated. Then quietly, “I should’ve caught this earlier. I should’ve noticed something was wrong before it got this far.”

Donnie reached for him weakly. His fingers curled around Leo’s forearm, light but grounding. “You did catch it. And you fixed it.”

“Barely,” Leo muttered.

“You saved me,” Donnie whispered. “And you always do.”

Leo bowed his head. His other hand came to rest over Donnie’s. He didn’t say anything for a long time. He just stayed there—eyes closed, twin to twin, breathing in sync.

And for a moment, the world was quiet.

Later, when Donnie was resting in his cot with a heated blanket draped over him and Leo sitting on the floor nearby, still watching his vitals, Mikey and Raph finally slipped in. They were silent as they entered, faces tight with concern, but relaxed the moment they saw Donnie breathing steady, color returning to his cheeks.

“He’s okay?” Raph asked, voice just above a whisper.

Leo nodded. “Yeah. For now.”

They all huddled close after that—silent, protective, exhausted—but relieved.

None of them knew it wouldn’t last.

But for that night, Donnie was safe.

.

.

.

The lab lights were dimmed to a soft, golden hue. The harsh blue fluorescents were too much for Donnie’s recovering senses, and Leo had insisted on adjusting them—along with every other setting in the room.

Blankets were brought in. A humidifier. Noise-canceling walls. An anti-sensory overload cocoon of safety.
Donnie called it overkill.
Leo called it necessary.
The others called it Leo being Leo now.

Donnie lay on his side in the padded recovery cot, swaddled like a stubborn burrito. His bandaged shell still ached, and the phantom feeling of something crawling beneath his plates hadn’t fully faded—but it was better. Better than the itch. Better than the fear.

For the first time in weeks, his body wasn’t screaming.

Across from him, Leo sat in a rolling chair with his feet propped up on a nearby table. His head was tipped back, mouth slightly open. Asleep, finally.
Despite being the older twin, he looked younger like that.

Donnie watched him in silence for a moment.
He could see the new stress lines on Leo’s face, could see the slight tremble still lingering in his fingers, even in rest. Leo hadn’t left his side once since the procedure. Not even to sleep. Donnie had tried to shoo him off more than once, but the most he got was a grumbled, “I’m not moving unless you make me,” before Leo slumped deeper into the chair and shut his eyes.

Donnie sighed. Quietly. Fondly.

“You know,” he murmured into the quiet, “you’re going to give yourself a spinal curve worse than mine if you keep sleeping in that position.”

Leo stirred but didn’t open his eyes. “Not moving.”

“You’re the worst patient I’ve never had.”

Leo cracked an eye open now. “I’m not the patient, you are.”

“Could’ve fooled me,” Donnie said, then after a beat: “You look awful.”

“Thank you.” Leo rubbed his face, then blinked the sleep away and sat up straighter. “How are you feeling?”

Donnie considered. “Like someone dug around inside my spinal ridge with a laser scalpel.”

Leo frowned. “Yeah, that tracks.”

“But,” Donnie added, voice softening, “also like I can finally breathe again.”

A silence followed. Comfortable. Weighted.

Leo stood and moved closer, kneeling beside the cot so he was level with Donnie’s gaze. For a moment, the confident leader act faded. He looked just like the boy Donnie had grown up beside—terrified of losing people, terrified of being left behind.

“I really thought I was gonna lose you,” Leo whispered.

Donnie met his eyes. “I know.”

Leo hesitated. “I’ve been trying to figure out what I’d do if something ever happened to you, and—every time I try, I can’t. I literally can’t picture it.”

Donnie stared at him, throat tight. “That’s because you’re not meant to.”

A faint smile tugged at Leo’s lips.

Donnie reached out and tapped Leo’s forehead lightly. “You’re stuck with me, remember? Twin contract. Mutual irritation and undying loyalty, forever.”

Leo huffed a quiet laugh, eyes shining. “Right. Forgot that was in the fine print.”

Donnie leaned back into the cot, eyelids heavy. “We should get a lawyer to rewrite it. Add some clauses. No more letting alien matter hijack our bodies. No more solo heroics. No more…” His words slurred with sleep. “No more leaving each other behind.”

Leo’s voice was gentle. “Deal.”

Donnie was almost asleep when he felt Leo’s hand—warm and steady—wrap gently around his. Just like the night before.

And Leo, in a voice barely audible, whispered:
“I’ll always be there when you need me. No matter what happens next.”

Donnie didn’t answer.

He didn’t need to.

Chapter Text

At first, Leo thought it was nothing.
A few extra sneezes. A little fatigue. Donnie blamed it on the aftereffects of the procedure—his immune system was working overtime, his nerves were still recovering, and post-op symptoms were normal.

He was healing. That’s what everyone said.
That’s what Leo told himself.
That’s what Donnie insisted.

So when Donnie started coughing, no one panicked.

Not at first.

It was late at night when it happened.

Leo had gotten used to checking on Donnie at night. Sometimes, Donnie would be curled up asleep in his recovery cot with his face squished awkwardly into a pillow, snoring softly. Other nights, he was wide awake with a datapad resting on his chest, muttering through half-baked algorithms and energy readings, trying to stay sharp.

But tonight was different.

Tonight, Leo opened Donnie's lab door and heard it immediately—the rough, wet sound of coughing echoing from the corner bathroom.

Leo was moving before he even realized it.

He pushed open the bathroom door to find Donnie doubled over the sink, one hand gripping the porcelain so tightly his fingers had gone white. His shell was shaking with each breath, each cough—raw and heaving. Leo’s eyes dropped to the basin.

And froze.

Red.

Bright, unmistakable, wet.

Blood.

Spattered across the porcelain. Staining the drain.
Donnie was coughing up blood.

Leo surged forward. “Donnie—Don, hey—breathe, breathe, you’re okay—”

“I’m fine,” Donnie rasped, his voice shredded at the edges. He tried to straighten up, but another cough bent him double, and more blood hit the sink. “Just—just a scratchy throat. Probably—hah—microscopic scar tissue—”

“Don’t,” Leo said, voice low, urgent. “Don’t brush this off.”

“I’m—” Donnie swallowed hard. His knees buckled, and Leo caught him before he hit the tile. “I’m not brushing it off,” he admitted, weaker now. “I just… didn’t want to scare you.”

“Well, too late for that,” Leo snapped, and then immediately regretted it upon seeing the sad and scared look on Donnie's face. Leo softened. His twin was scared and in pain. Now was not the time to be upset “Come on. Sit down. Let me look at you.”

He dragged Donnie back to the cot, moving fast but careful. The blood was still on Donnie’s chin, and Leo’s stomach twisted as he wiped it away with trembling fingers.

Donnie was burning up.

“Okay,” Leo muttered, grabbing a scanner. “Okay, it’s fine, we just—maybe there’s an infection. Post-op inflammation. Maybe a vessel got nicked. Maybe—maybe—”

He scanned once. Then again. Then again.

Each result looked worse than the last.

“Leo?” Donnie rasped.

Leo didn’t answer. He was already grabbing his phone and dialing the one person that he knew could help them, no matter how much Leo hate to admit it

“Draxum. Get here. Now.”

Ten minutes later, Draxum was there. And this time, he wasn’t calm. Not even close.

He examined the samples. Ran the vitals. Pulled blood and tissue, read through Leo’s scans twice. His eyes narrowed, jaw clenched tighter with each passing second.

Leo hovered just over his shoulder, watching everything, trying not to fall apart.

Finally, Draxum stood and turned to them both. His tone was grim.

“There’s something wrong with the cellular regeneration patterns.”

Donnie was pale but alert. “Meaning?”

“Meaning the Krang matter didn’t just embed—it altered something. There’s uncontrolled replication in your white blood cells. Mutated ones.”

Leo felt ice creep down his spine.

Donnie blinked. “Wait. Like—cancer?”

Draxum hesitated. Just a second. Then gave a sharp, definitive nod.

Leo’s knees nearly gave out.

The room was silent.

Donnie’s voice was steady, but too quiet. “How bad is it?”

Draxum exhaled slowly. “It’s rare. Aggressive. The mutation likely began before the removal—dormant, undetected. The surgery triggered something. A chain reaction.”

Leo stepped forward, jaw clenched. “What’s the prognosis?”

Draxum met his eyes. “I don’t know yet. We need to begin treatment immediately. But make no mistake—this will be a war.”

Later, when the lab cleared and the scans stopped beeping and Draxum stepped away to begin synthesizing treatment protocols, Leo sat beside Donnie’s bed, both of them wrapped in silence.

Donnie didn’t cry.

He didn’t panic.

He just stared at the ceiling, lips pressed tight, as if daring himself to be strong.

Leo, on the other hand, was unraveling at the seams.

“I thought I fixed it,” he whispered. “I thought I saved you.”

Donnie turned his head slowly, met his brother’s broken stare.

“You did,” he whispered back. “You gave me time.”

Leo’s hands trembled in his lap.

Donnie reached out and took one, squeezing it tight.

“And now you’re gonna give me more,” he said, voice fragile but certain. “We’re gonna beat this. Together.”

Leo blinked fast.

And nodded.

Even though every part of him was screaming.

Chapter Text

Draxum stood at the edge of the med bay, arms crossed, waiting.

He didn’t wait often. He wasn’t a patient man by nature. But this wasn’t impatience.

It was respect.

Across the room, Leonardo sat beside Donatello’s cot, curled forward with his elbows on his knees, head bowed, fingers clenched together like they were the only thing holding him up. His shoulders were tense—too still for comfort.

Donatello lay against the cot’s raised cushions, a blanket over his legs, vitals steady but fragile. His eyes were open, but distant, unfocused. Every so often, they blinked like he was coming back from somewhere else.
Somewhere darker.

Neither twin had said a word in a while.

The news had settled into the room like smoke. Stifling. Unmoving.

“I have to tell them,” Draxum said gently. “Your family. They will want to know.”

Donnie’s eyes flicked toward him. “No.”

Leo immediately echoed, “No.”

Draxum stepped forward. “They deserve to know.”

“Which is why we don’t want to tell them,” Leo muttered, voice low, broken around the edges.

Donnie gave a short, bitter breath. “They’ve just started to feel normal again. They’re laughing again. They’re… healing.”

“I’m not going to rip that out from under them,” Leo added. “Not yet.”

Draxum looked between them.

Leo wasn’t crying. He hadn’t let himself yet. But his voice was cracking. And Donnie looked like someone had unplugged him—wired into silence and fear, barely holding himself together.

The twins weren’t denying the truth. They weren’t avoiding it.
They just couldn’t carry it.

Not alone.

“I understand,” Draxum said at last. “But you cannot go through this without them. And they would not want to be kept in the dark.”

The silence returned. The weight of it pressed down like gravity.

Finally, Donnie whispered, “We don’t have the words.”

Leo’s jaw tightened.

Donnie reached out—still weak, still shaking—and touched Leo’s wrist. “We can’t say it, Leo.”

Leo didn’t look at him. Just nodded. Barely.

Draxum took a quiet breath and approached, kneeling beside the cot. He kept his voice low. “Then allow me.”

Donnie didn’t speak, but his grip on Leo’s wrist tightened.

Leo finally looked at Draxum.

His voice was hoarse. “Please.”

The next room over was the dojo.

Splinter was meditating when Draxum entered—though he stood immediately. Raph, Mikey, and April were nearby, chatting softly until they saw the expression on Draxum’s face.

April’s smile vanished.
Raph straightened.
Mikey went still.

Draxum took a breath. And told them.

It was April who cried first. Softly, hands trembling over her mouth.
Mikey followed, a gasp of disbelief escaping him like a crack in porcelain.
Raph didn’t make a sound—just backed up, as if the news had physically struck him, and turned away, fists clenched, shaking.

Splinter said nothing. But his gaze dropped, and his body swayed faintly, like someone had cut his strings.

They all asked the same question in different ways:

“What do we do now?”

And Draxum, for once, had no answer.

Back in the medbay, Leo was still sitting at Donnie’s side. He hadn’t moved. His hand was still wrapped gently around his twin’s, both of them clinging to that shared touch like it was a lifeline.

Donnie was finally asleep. Not peacefully—but asleep.

And Leo sat frozen, like if he moved, the weight would crush him.

The door hissed open softly.

Draxum entered and paused just inside. “They know.”

Leo nodded, not looking up. “How’d they take it?”

“They’re here for you,” Draxum said, not really answering his question. “Both of you.”

Leo’s voice dropped. “They don’t deserve this.”

Draxum didn’t answer. There wasn’t an answer for that.

After a beat, he left them alone again.

Donatello was awake when they came.

He didn’t look it, not at first—eyes half-lidded, breath shallow, blanket tucked under his chin like a shield—but he had heard their footsteps coming down the hall, and his heart had already begun to thud uncomfortably in his chest.

Not from sickness.

From dread.

He had tried to picture this moment. Tried to imagine what it would feel like when they finally knew. Tried to come up with a script. A joke. A way to make it easier.

But there was nothing.

The medbay door opened with a quiet hiss.

Raph came in first, followed by Mikey, April, and finally Splinter. None of them said anything for a moment.

They just stood there, staring at him like he might break if they stepped too close.

And maybe he would.

“Hey,” Donnie rasped, trying to summon a smile. It hurt. “So… you guys heard.”

No one laughed. Not even Mikey.

“Y-yeah,” Mikey said, voice thin.

Donnie’s eyes flicked toward Raph. He looked smaller than usual. Tense. His shoulders were tight and his eyes were red—but dry. He stayed near the back, like if he got too close, this would all become too real.

April moved first. She walked to Donnie’s side and sat gently on the edge of the cot, brushing her thumb along Donnie's brow. “You could’ve told us,” she said softly.

Donnie’s voice caught. “We wanted to.”

“But you didn’t,” Raph said, his voice thick and low. “Because you didn’t want us to hurt.”

Donnie looked away. “I didn’t want to be the reason you broke again.”

A beat of silence.

Then a weight dropped onto the cot—Mikey, curling gently beside Donnie like he used to when they were kids. His arms wrapped around his brother’s shoulders, careful but firm.

“You’re not a burden,” Mikey whispered. “You never could be.”

Donnie let out a shaky breath.

Splinter stepped forward next. His hands clasped behind his back, his expression unreadable. “I do not have words to ease this pain, my son,” he said quietly. “But I am here. We all are. And we will not leave you to face this alone.”

Donnie turned his head slowly, watching them.

April still holding his hand.
Mikey curled up beside him.
Raph near the foot of the cot, fists shaking as he fought to stay composed.
Splinter standing like a stone—steady and quiet.

And just behind them, leaning against the wall, Leo. Arms folded. Head down. Silent, but watching every movement with red-rimmed eyes.

Donnie blinked hard. “I’m scared,” he admitted, voice barely a whisper.

It cracked something open in the room.

Raph finally stepped forward and sat beside his legs, head bowed. One massive hand rested on Donnie’s ankle, grounding. Mikey didn’t move, just hugged tighter.

“I know,” Raph said. “We all are.”

“But we’ve been through worse,” Mikey added softly.

April nodded. “And you’re not doing this alone.”

Splinter gave a solemn nod. “We are Hamato. And Hamato does not abandon its own. Anatawa Hitorijani”

Leo hadn’t moved.

Donnie reached for him. “Leo…”

Leo walked forward without a word and lowered himself next to the cot, slipping into the space between April and Raph, his head resting gently beside Donnie’s on the edge of the mattress. He didn’t say anything.

He didn’t have to.

Donnie reached over and tangled their fingers together.

For a long time, none of them spoke. They just sat there in the dimmed medbay, surrounded by soft beeps and glowing monitors, wrapped in blankets and quiet promises.

They couldn’t take it away.
They couldn’t undo it.
But they could be there.

And that was everything.

Later, when the medbay lights dimmed for the evening cycle, Leo sat in the dark. The machines whirred quietly around him, Donnie still resting behind him, unaware of the sound of quiet, broken breathing that eventually escaped his brother’s throat.

Leo hunched forward, hands over his face.

And cried.

Not loudly. Not dramatically. Just… quietly.

Like he was trying to hide it from the world.
Like he didn’t want Donnie to hear.
Like he didn’t know what else to do.

And in the faint blue glow of monitors and heartbeat trackers, Leo’s tears fell silently into the space between his knees—hot, sharp, and endless.

He couldn’t save his twin.

Not yet.

But he would try. No matter what it took

Chapter Text

The room was quiet—clinical, controlled.
But the silence wasn’t peaceful.

Donnie sat propped against a pile of pillows on a reinforced cot, a blanket around his shoulders, an IV pole beside him. The port in his arm was already connected to a slow drip of glowing pale-blue fluid, which was Draxum’s synthesized chemotherapy compound, modified for mutant physiology and Krang-induced cellular mutations.

It wasn’t just chemo. It was custom alchemy.
And still, they didn’t know if it would work.

Leo stood nearby, arms crossed, watching every rise and fall of Donnie’s chest like it was a countdown. He hadn’t slept in over a day—not really—and there was a twitch behind his eye that said the exhaustion was catching up. But he wouldn’t move.

He hadn’t left Donnie’s side since the first bloody cough.

Not even once.

“You don’t have to hover,” Donnie said, voice faint but dry. “I’m not going to spontaneously combust. Pretty sure the chemo’s not that experimental.”

Leo didn’t budge.

“You say that,” he replied, “but we both know your body’s allergic to normalcy.”

Donnie smirked, though it was weak. “Fair.”

Leo took a step forward and gently tucked the blanket closer around Donnie’s sides, careful of the IV line. “How do you feel?”

Donnie sighed, eyes flicking up to the bag above. “Like something cold is crawling through my veins and setting up tiny demolition charges.”

Leo’s jaw clenched. “You want me to stop it?”

“No,” Donnie said. “I want it to work.”

Mikey was the first to visit that day.

He entered carrying a tray of warm soup and crackers, his smile small but genuine. “Got the good broth, bro. Even made it with your protein powder.”

Donnie arched a brow. “The purple one?”

Mikey held up a finger. “Relax, I only used half a scoop. I wasn’t trying to make pudding.”

Leo gently accepted the tray from Mikey. “Thanks, Mikey. He needs to eat.”

Donnie groaned. “He’s gotten bossier, hasn’t he?”

Mikey snorted. “Oh yeah. He’s basically Mother Hen now. Acting more and more like Raph every day. I think he is even developing a Raph-Chasm”

Donnie and Mikey expected Leo to act dramatic and offended by the accusation...or to even make a funny joke about his supposed 'Raph-chasm'

However, Leo didn’t respond

He just held a spoon up to Donnie’s lips like it was non-negotiable.

Donnie was a little upset to not even hear a laugh nor see a smile from his twin.

With a sigh, he opened his mouth, grumbling all the way.

Later, Raph came in and sat beside the cot without a word. He didn’t say much. He didn’t need to. His presence was enough. He watched the drip. Watched Donnie. Sometimes reached out and held his hand. Sometimes closed his eyes and just sat in the stillness.

Leo stayed through it all, perched like a guard dog, alert and unmoving.

Even when Mikey returned with blankets.
Even when Splinter came and whispered something in Donnie’s ear that made the scientist’s eyes shimmer, even though he didn’t cry.

Even when the vomiting started later that night.

It hit fast.

Donnie had been mid-sentence—something snarky about Leo’s refusal to eat unless Donnie did—when he went pale. His hand clutched at the cot’s edge.

“Leo,” he croaked.

Leo didn’t need more. He was already holding the basin before Donnie doubled over.

It was awful.

The sound. The shaking. The way Donnie clenched his jaw to keep from crying out. Leo held one arm around his back and gently pressed a damp cloth to his forehead. “It’s okay. I’ve got you. Just breathe. You’re okay.”

Donnie coughed again. This time, nothing came up.

“I hate this,” he gasped. “I hate this so much.”

“I know,” Leo whispered, his voice cracked and gentle. “Me too.”

Hours later, when Donnie had finally passed out, Leo remained sitting on the edge of the cot, watching him.

Draxum entered briefly to record vitals and update notes. He gave Leo a passing look. “You need rest.”

Leo shook his head. “Later.”

Draxum stared at him. “You cannot pour from an empty cup.”

“I’ll find a new cup,” Leo replied.

Draxum almost looked impressed. Almost.

That night, Leo finally allowed himself to sleep—barely.

He curled beside Donnie on the cot, one arm loosely draped over his twin’s shoulders, his other hand gripping Donnie’s tightly.

And when Donnie stirred from another chemo fever-dream, flinching with a low whimper, Leo was already awake, already whispering, “I’m here. You’re okay. I’ve got you.”

And he did.

Because Leonardo Hamato had a mission now.
One more important than any battle, any villain, any redemption arc.

He was going to keep Donnie alive.

No matter what it took.

Chapter Text

Two weeks into treatment, things began to spiral.

The chemo was supposed to help—slow the mutation, stabilize Donnie’s cells, give Draxum more time to develop a tailored cure. And for a while, it did.

But then the numbers changed.

And not in the right direction.

Leo sat at the edge of the lab console, hands covered in ink from Draxum’s spellwork and blood from a sample run gone wrong. His eyes scanned the readings again—again—and again. Each time, they told him the same thing.

The cancer was winning.

Not fast. Not in a dramatic collapse. But like a leak in a boat. Silent, steady. Unstoppable.

Every drop of Donnie’s strength was slowly draining through a crack they couldn’t patch.

And Leo felt like he was drowning with it.

Donnie had good days. Days where he could sit up and do equations in his head, roast Leo’s hoodie choices, complain about the weird aftertaste of magic-enhanced broth, curtosey of Mikey. Days where he was Donnie again.

And then there were the other days.

Where he couldn’t hold a stylus.
Where he was too weak to speak.
Where his eyes barely opened and his skin was cold and waxy and pale.

Leo memorized every symptom, every sigh, every shiver. He kept the chart. The meds. The hydration schedule. He carried Donnie to the bathroom. He helped change his bandages. He even timed his breathing against Donnie’s in the middle of the night—just to be sure.

And all the while, Leo’s mind was racing.

He wasn’t just a brother anymore. He was a protector. A nurse. A student of Draxum’s biochemical teachings.
A soldier in a war with no mercy.

One night, when the fever peaked again, Donnie thrashed in the cot, coughing into a towel and curling in on himself. Leo was at his side in seconds, pressing a damp cloth to his neck, trying to cool his skin down.

“It’s okay,” Leo said quietly. “It’s just the treatment again. You’re okay.”

Donnie’s voice was barely audible. “Hurts…”

“I know.” Leo bit his lip. “I know. Just hold on. We’re close.”

But they weren’t.

And Leo knew it.

The next morning, Leo stormed into Donnie's lab, which had now become Draxum's workspace.

His voice was calm. Too calm.

“We need to try something else.”

Draxum didn’t look up from the scans. “This is the most stable compound we’ve synthesized. To push beyond this would—”

“It’s not working,” Leo snapped. “His blood count dropped again. His fever won’t break. His weight’s down another five pounds. His cells are still mutating—just slower.”

Draxum exhaled. “Slower is progress.”

Leo’s fists clenched. “It’s not enough.”

That finally made Draxum meet his eyes.

And something in Leo cracked.

“Please,” Leo said, voice breaking. “You’ve done things I’ve never dreamed of—hybrid formulas, mystic fusions, forbidden research. You created us, for crying out loud. There has to be something we haven’t tried. Some version. Some risk.”

Draxum studied him. “You would risk harming your brother further with an unstable prototype?”

Leo didn’t hesitate.

“I’ll risk anything to save him.”

That night, Leo combed through every note, every spellwork scroll, every lab report Donnie had ever written.

He laid it all out across the floor of the lab like pieces to a puzzle only he could solve.
And even as his hands shook, even as exhaustion weighed down his limbs and grief curled around his chest like a vice—

Leo worked.

Because Donnie was still alive.

And Leo wasn’t going to let that change.

Not if he had any say in it.

.

.

.

The medbay was silent except for the hum of machines and the gentle drip of fluids through Donnie’s IV.

It was late. The kind of late where time blurred, where even the soft glow of monitors seemed too loud. Donnie had been asleep for hours—finally drifting off after a relentless fever, his breathing now steady, albeit shallow.

Leo sat across the room, half-lit by the bluish monitor light. His body was curled forward, arms braced against the counter, head bowed. In his hands were a stack of notes and chemical breakdowns—pages full of crossed-out equations and half-finished spell matrixes.

His eyes were red. Not from crying. Not anymore.
From staring too long. From not blinking. From trying.

Trying to do the impossible.

Trying to save his twin.

A sharp breath broke from him, the first crack in the dam. His fingers trembled and clenched into the paper, and then—quietly, like a slow spill—he broke.

A low, strangled sob escaped his throat. He curled forward, shaking, biting down on his own hand to muffle the sound. His whole body shook with the weight of everything he hadn’t said, everything he couldn’t fix, every day he watched Donnie get worse no matter what he did.

And he thought he was alone.

But he wasn’t.

“...Leo?”

The voice was faint. Dry. Barely there.

Leo jerked his head up, eyes wide, guilt slamming into his chest like a tidal wave. “Don—”

Donnie was half-upright in his cot, blanket slipping off his shoulder, one hand reaching weakly toward him. His brow was furrowed with concern—not pain.

Concern for Leo.

Leo scrambled to his feet, wiping at his eyes. “You—you should be asleep. Sorry, I didn’t mean to wake you—”

“You didn’t,” Donnie whispered. “You were crying.”

Leo turned away. “I wasn’t.”

“Liar.”

Donnie’s voice was so quiet it nearly didn’t exist, but it was steady. And worse—gentle.

Leo swallowed hard, still facing away. “You shouldn’t see me like that.”

Donnie blinked slowly. “Why not?”

“Because,” Leo said, forcing his voice to be even, “you’re the one who’s sick. Not me. I’m supposed to be strong for you.”

“You are strong,” Donnie said. “But that doesn’t mean you have to be okay all the time.”

Leo didn’t answer.

After a pause, Donnie reached out again. “Come here.”

Leo hesitated, shaking slightly. Then he crossed the room and sat beside the bed. Donnie scooted, just enough to make space. It took all his strength—but he did it. And when Leo sat, Donnie wrapped both arms around him, pulling him down until Leo’s head rested against his chest.

Donnie held him.

Leo went rigid. He didn’t want to cry again. He didn’t want Donnie to see him like this, feel how terrified he was. But his twin’s arms were warm. Steady. And the steady rhythm of Donnie’s heart—

Leo’s body finally relaxed.

“I hate seeing you like this,” Donnie whispered. “You’re burning yourself out, Leo. You haven’t slept more than an hour at a time. You barely eat. You won’t let anyone else help.”

“I can’t,” Leo said hoarsely. “If I stop, even for a second—”

“I won’t die because you took a nap,” Donnie interrupted gently. “And I won’t live better if you kill yourself taking care of me.”

Leo closed his eyes, throat tight.

“You don’t have to do this alone,” Donnie whispered. “Mikey, Raph, Dad, April, heck even Draxum… they’re all here. They want to help. Let them.”

Leo shook his head against Donnie’s chest. “I can’t lose you.”

“I know,” Donnie murmured, resting his cheek on Leo’s head. “But even if… even if this doesn’t go the way we want, I want you to be okay.”

“Don’t say that,” Leo said, voice cracking.

“I need you to promise me,” Donnie whispered. “That no matter what happens… you’ll be with me. Not as my nurse. Not as my shield. Just… as my brother. My twin.”

Leo trembled.

“I want you here,” Donnie said, pressing his forehead to Leo’s. “I want to feel your heartbeat next to mine. I want to laugh with you. I want to look at the stars and argue about who’s smarter. I want to be us, for as long as we can. And if that time is short… then let it be real.”

Leo couldn’t speak.

The weight of what Donnie said pressed into his chest like a thousand bricks. He hated the implication. Hated how Donnie was already thinking about the end. But he didn’t argue.

He didn’t tell him to stop.

He just pressed closer, curling into his twin’s warmth like it was the only thing keeping him together.

Donnie held him.

Neither spoke again.

And in the quiet hum of the med bay, the twins just breathed in sync—heartbeats touching, fear ebbing and flowing, love between them like gravity.

Chapter Text

The quiet moment didn’t last.

Donnie was asleep again by morning, curled on his side with a blanket pulled high and a soft whimper barely escaping his throat with every exhale. His fever had dipped, but his vitals were unsteady.

Another bad night.
Another checkmark on Leo’s spiraling chart.
Another confirmation that the chemo wasn’t enough.

Leo sat nearby, notebook in hand, red ink scrawled messily over the margins—circles, theories, desperate thoughts that barely made sense.

He didn’t care.

The door hissed open behind him.

“You look like you’ve lost your mind,” Draxum said without preamble.

Leo didn’t look up. “I might have.”

Draxum walked forward, scanning Donnie with a flick of his wrist. “His fever is holding. That’s good.”

“It’s not enough,” Leo whispered.

Draxum said nothing.

“I can’t keep waiting for him to fail before we act,” Leo went on, voice shaking but controlled. “He’s going to die if we keep waiting. You know that.”

“I’m working on the next compound—”

“Then let’s try it now.”

Draxum paused. “It’s unstable.”

“I know.”

“It could accelerate the cancer.”

Leo turned now, eyes bloodshot but focused. “And doing nothing will kill him just the same.”

Draxum studied him.

“You don’t understand,” Leo said, low and strained. “He’s not just my brother. He’s my twin. We’re two halves of the same whole. If I lose him, I don’t… I don’t know who I am after that. I don't know how to be me without him”

Draxum’s expression softened. Slightly.

Leo stepped forward, pulling a page from his notebook. “I took your notes. I rewrote the blood compatibility matrix. Look—if we bond it with a mystic stabilizer from the Krang serum, we might get a controlled mutation. It could target the damaged cells and leave the rest alone.”

“And it might kill him on the spot,” Draxum said flatly.

Leo’s voice dropped. “But it might save him.”

A silence fell between them.

Then, quietly, Draxum asked, “You want to do this behind your family’s back?”

Leo nodded once. “They’ll say no. They’ll want to wait. And I… I can’t wait anymore.”

Draxum narrowed his eyes. “Then we’ll do it tonight. When everyone is asleep.”

That evening, after April had left, after Mikey brought tea and Raph tucked another blanket around Donnie’s feet, after Splinter kissed Donnie’s forehead and whispered “sleep well, my son”—

After everyone was gone…

Leo stayed behind.

Donnie was breathing quietly. His brow was smooth for once. No fever. No pain. Just rest.

Leo reached forward and brushed his thumb along Donnie's cheek. “I’m sorry,” he whispered. “You told me to stop pushing. But I can’t. I love you too much to just let this happen.” Then Leo fully cupped Donnie's cheek, bending down to leave a gentle kiss there "I can't lose you"

He lingered for a moment longer.

Then he turned to Draxum, who stood at the bench, syringe in hand. Inside: a shimmering silver serum with flecks of purple and gold. The prototype.

No label. No name.

Only a chance.

Leo held out his hand.

Draxum hesitated, then handed him the vial.

Leo knelt beside Donnie and gently touched his wrist.

“I’m right here,” he whispered, even though Donnie didn’t wake. “And I’m not going anywhere.”

He pressed the needle to the port in Donnie’s arm.

And pushed.

The change was immediate.

Donnie’s body jerked, just once. His eyes flicked open—but didn’t focus. His mouth parted, and a shuddering gasp left his lungs.

Leo reached out instantly, gripping his twin’s hand. “Donnie? Donnie—can you hear me?”

Donnie blinked slowly, breath ragged.

Then… stilled.

Leo felt his heart stopped

No...no he couldn't be...

Did Leo failed? Did Leo just watch his twin brother die before his eyes?

Draxum rushed to the monitors. “Vitals are rising—heart rate increasing—temperature spiking—he’s reacting.”

Leo hovered, trying not to panic. “Is it too much? Is he—?!” Leo couldn't even finish the thought, not wanting to even consider death an option

Draxum’s eyes locked on the readout. “No… wait—he’s stabilizing. Cellular breakdown has slowed. Mutation… is responding.”

Leo’s breath caught.

Donnie’s body stopped shaking. His chest rose, then fell, slow and even. His brow smoothed. His fingers, still locked in Leo’s, twitched once—and then gently curled tighter around his brother’s hand.

Leo stared down at him.

Draxum straightened. “It’s working.”

Leo didn’t cry.

Not this time.

But dang did he want to so badly

Not out of sadness, but of relief that his baby twin had managed to pull through

Leo pressed Donnie’s hand to his beak before bringing it his forehead and whispered, “Please stay with me.”

Because this was only the beginning.

.

.

.

The room had gone still again.
But this time, it wasn’t because of death.
It was because of breath.

Steady. Real. Present.

Donnie was asleep now—breathing deeply, arms relaxed against the mattress, skin cool instead of clammy. No fever. No convulsions. His heart was beating. Slower than usual, but strong.

Alive.

And Leo hadn’t moved for almost an hour.

He sat on the edge of the cot at first, just… staring. Watching every rise and fall of Donnie’s chest like it might vanish again if he blinked too long.

His mind kept replaying it—the moment it all stopped.

The moment Donnie went still.

The way his lungs refused to move.
The way his body sagged like someone cut the strings.
The way Leo's mind and heart almost ceased to function

Because for a second, Leo thought...

He’s gone.

For that second—eternal and unbearable—Leo was convinced he had done it. That he had made the call. That he’d pushed too far. That he’d killed him.

His baby twin.

His Donnie.

The only person who knew every beat of his heart from the inside out. His other half. His partner in chaos and creation. The one person Leo had always protected, even when the world burned around them.

And he thought it was over.
That all he’d have left were memories and the feeling of Donnie’s body going cold in his arms.

But he was wrong.

Leo lay down beside him now, curled protectively around Donnie’s side, one hand resting lightly on his chest. He could feel it—his brother’s heartbeat. Slow. Rhythmic. Alive.

A tear slid down Leo’s cheek before he could stop it.

He pressed his forehead to Donnie’s shoulder, breathing him in like he might disappear again.

“You’re still here,” Leo whispered.

His voice cracked. He reached out and smoothed a hand over Donnie’s temple, before moving down to rest it against the back of Donnie's nape. Then, gently, he kissed the top of his twin’s forehead.

“I thought I lost you,” he whispered. “I thought I… I was too late.”

His voice was almost inaudible now.

“But you stayed.”

Leo let out a shaky breath and pulled the blanket tighter around them both. His arm slid around Donnie’s waist, holding him carefully, reverently.

“One more day,” Leo whispered into the quiet. “That’s all I ever ask. One more day with you.”

He tucked himself close, feeling Donnie’s warmth, his heartbeat, the familiar rise and fall of his breath. The fear was still there, coiled deep in Leo’s gut, whispering about risks and unknown consequences.

But for now, Donnie was still breathing.
And Leo would cling to that with everything he had.

“Sleep easy, Dee,” he murmured. “I’ve got you. I’ll always have you.”

And slowly—finally—Leo let his eyes drift closed, his breathing syncing with his twin’s, unaware of the subtle flicker beginning in Donnie’s bloodstream.

A ripple of something new.

Something unseen.

Something coming.

Chapter Text

The morning light filtered in through the lab’s tinted windows, casting pale stripes across the floor. The monitors hummed softly, steady in their rhythm. Peaceful.

Donnie stirred first.

His fingers twitched.

Then his arm.

Then his eyes blinked open—slow, unfocused, searching. He lay there, breathing evenly, vision taking time to adjust to the softened light.

He didn’t feel sick. Not like before. No wave of nausea. No pounding headache. No crushing fatigue.

Just… strange.

Detached.

Light.

Too much light.

His limbs didn’t ache. His chest didn’t burn. But his body felt off, like something inside him had been rearranged. Like wires had been spliced differently, rerouted without permission.

Something wasn’t right.

Beside him, Leo was still asleep—curled close, arm gently slung over Donnie’s waist, face pressed against his shoulder. There was a faint crease between his brows, even in rest. Tension never fully leaving him.

Donnie looked at him. Really looked.

And something tugged at the edge of his awareness.

Recognition, yes. But…

Distance.

Not emotional. Cognitive.

He knew this was Leo. His twin. His other half.

But it took him an extra second to feel that truth. Like a memory buffering, like a program loading just a beat too late.

A pulse of alarm flickered through him.

His eyes drifted upward, toward the ceiling.

And in the dim reflection of the light panel above, he saw his own eyes—

—and they were glowing.

The heart monitor spiked.

Leo stirred.

And Donnie whispered, almost without thinking: “Leo.”

It was barely audible.

But Leo shot up like he’d been electrocuted.

“Donnie?” he gasped, wide-eyed. “You’re—oh my gosh—you’re awake—”

Donnie stared at him, still and unblinking. “Something’s wrong.”

Leo’s heart dropped. “What? What is it—what hurts?”

Donnie didn’t answer immediately.

He lifted one hand and turned it in front of his face, examining the fingers like they weren’t his. His pupils pulsed with faint violet light. His breathing remained steady—but his skin had an odd shimmer to it, like residual mystic energy was clinging to him, running beneath the surface.

Leo reached out slowly. “Donnie…”

Donnie flinched.

Leo froze.

Donnie blinked, frowning now. “Sorry. I… didn’t mean to.”

Leo’s heart was pounding. “Okay. Okay, it’s fine. You’re just disoriented. Draxum said there could be aftereffects—”

“I remember the serum,” Donnie said, voice low

This made Leo freeze and his heart did a double take. “You do?” Leo asked cautiously

“I remember and felt it. Don’t worry I’m not mad or anything. And then… nothing. I thought that meant that the serum actually cured the cancer. And maybe it still did but now I feel…weird?.”

“Your heart stopped for a second,” Leo whispered. “I thought I—”

He didn’t finish. His hands were trembling again.

But Donnie just looked back at him. Something in his gaze was too sharp. Not cold, but precise. Clinical. Like he was scanning Leo, measuring him, data flashing behind his eyes.

“Are you okay?” Donnie asked suddenly.

The question caught Leo off-guard. “Me?”

“Yes. You haven’t slept. Your vitals are irregular. You’ve lost weight. I can hear it in your pulse.”

Leo blinked. “You can hear—?”

Draxum entered the room just then, expression neutral—but alert. “I saw the spike. He’s awake?”

Donnie looked over at him. Eyes narrowing. “Something’s wrong with me.”

“I am aware,” Draxum said calmly, approaching with a scanner. “Let me take your vitals.”

“I already know them,” Donnie replied, voice distant. “Blood pressure elevated. Respiration normal. Heart rate sixty-eight beats per minute. Theta brainwave activity—fluctuating.”

Leo stared.

Draxum blinked. “How do you—?”

“I don’t know,” Donnie said. “But I can feel it.”

He looked down at his hands again. “My nervous system is behaving like an antenna. My skin reacts to the electromagnetic fields in the room. My thoughts are… louder.”

Leo stepped forward. “Donnie, you’re kind of scaring me.”

Donnie looked at him again. For a moment, there was something familiar—soft—in his gaze. “I’m sorry. I don’t mean to.” Then his voice became quiet. “I’m honestly scaring myself too”

“Then what’s happening?”

Donnie’s voice dropped to a whisper. “I think… the serum changed me.”

Draxum’s tests were silent but swift. The readings flashed with results neither he nor Leo fully understood yet. But what was clear—even to them—was that Donnie’s DNA had been altered.

Slightly.

But permanently.

Leo stood just outside the med bay curtain, pacing, running his hands down his face again and again.

Donnie was alive.

But changed.

And Leo didn’t know what it meant.

Was this a new evolution? A step toward recovery? Or had he traded one danger for another?

Had he made things worse?

Back behind the curtain, Donnie stared at his fingers. The glow had faded now, but he could still feel it. Like something was humming beneath his skin. A new layer of awareness. A connection to something he hadn’t yet defined.

And deep in his gut…

There was a whisper of fear.

Because for the first time since the diagnosis, Donnie wasn’t afraid of dying.

He was afraid of what he might become.

Chapter Text

Leo had pulled Donnie out of the med bay the moment Draxum gave the all-clear for mobility.

He didn’t take him far—just the old storage room that was placed between the med bay and Donnie's lab. It was quiet, hidden behind stacked boxes of forgotten tech, unused training mats, and board games missing too many pieces. The kind of place they used to sneak off to when they were younger, to avoid lectures, get away from Raph’s bossing, or just breathe.

Today, it was to breathe again.
But for a different reason entirely.

Donnie sat against the wall on a folded blanket, arms curled around his knees. Leo sat beside him, legs stretched out, head leaned back against the wall. His gaze was fixed on the ceiling.

Neither of them spoke for a long time.

The quiet buzz of fluorescent lighting above them and the low hum of the lair’s pipes filled the silence. It should’ve been peaceful.

But Donnie’s fingertips still tingled.
And Leo still hadn’t unclenched his jaw.

“...So,” Donnie finally said, voice thin. “This is new.”

Leo huffed out a humorless laugh. “That’s one word for it.”

“I’m not in pain,” Donnie added. “At least not in the same way.”

Leo turned to look at him. “But you feel different.”

Donnie nodded slowly. “Like someone rewired me while I was asleep. Like… like I’m not fully in control of my own thoughts. Everything’s fast and sharp and loud, but inside.”

Leo studied him. “You still feel like you?”

Donnie hesitated.

Then, quietly, “Mostly.”

Leo’s chest tightened.

Donnie looked down at his hands again. “I think the serum did more than target the cancer. I think it mutated me. It gave me a double mutation”

Leo’s voice dropped. “We knew it might. We understood the risks”

“But I didn’t expect it to work this well,” Donnie murmured. “I feel stronger, Leo. I feel… capable again. But that capability comes with static. Like I’m on the edge of something.”

Leo stayed quiet.

Donnie finally turned his head. “You shouldn’t have done it behind everyone’s back.”

“I know,” Leo said.

“You could’ve killed me.”

That defintely made Leo's heart stop for a second as he took in a shuddering breath, keeping his tears at bay, though his voice still came out small when he said “I know.”

Donnie sighed, resting his head on his arms. “But I’m still glad you did it.”

Leo blinked.

Donnie didn’t look at him, but his voice was honest. “If you hadn’t, I wouldn’t be sitting here. I’d be hooked up to another IV, barely conscious, counting breaths.”

“You’re still sick,” Leo said. “Just in a different way now.”

Donnie nodded. “But I’m awake. I’m here.”

Leo’s throat tightened. “You scared me so bad, Dee.”

Donnie looked over at him again, voice softer. “I know. You’ve been scared for a long time.”

Leo looked away, not wanting Donnie to see the tear that was falling down his face. It didn't stop his voice from cracking when he replied “I thought I’d lost you.”

Donnie reached out, quietly resting his hand over Leo’s, rubbing his thumb along the back of Leo's hand, knowing it's what always calm his twin down. “You didn’t.” his voice soft and certain

Leo looked back at his twin with sad eyes and was meet with a warm, but small smile. Leo gave him one in return as he looked down at their hands, watching Donnie make the soothing motion. Leo moved to move his finger over Donnie's, locking them together in like their version of a pinky promise

For a moment, neither spoke. The touch grounded them both.

But then—

It hit.

Suddenly, violently.

Donnie let go of Leo and jolted forward with a choked cry, grabbing at his head. His back arched, muscles spasming. A glow rippled over his arms, faint but undeniable—veins flickering violet beneath the skin.

“Donnie!” Leo scrambled forward, gripping his shoulders. “What’s happening?! What is it—?!”

“It’s—loud—everything’s loud—!” Donnie gasped. “I can hear electricity. The lights—the wires—your heartbeat—Leo it’s too much—!”

Leo tried to calm him, hands firm but gentle. “Okay, okay—breathe, Dee, I’ve got you—just breathe—”

But Donnie shook violently again. Sparks crackled from his fingertips, lighting up the shadows of the room. His eyes glowed faintly. His breathing hitched.

Leo felt the panic rise in his throat.

Then—

SLAM.

The door burst open.

Raph stood in the doorway, Mikey and April right behind him, all three wide-eyed and panting.

“We heard shouting—!” Mikey started, then froze. “What the—?!”

“Why is Donnie glowing?!” April cried.

Leo whipped around, still shielding Donnie. “Get Draxum—now!”

April bolted without another word.

Raph approached carefully. “What’s happening to him?”

Donnie let out another pained sound, curling into Leo. “I—I can’t stop it—it’s too much—”

Leo’s voice cracked as he held Donnie tighter. “It’s the serum. We pushed it too far—he’s reacting.”

Mikey stared, horrified. “Leo, what did you do?”

“I saved his life!” Leo snapped. He know Mikey was just confused and not really blaming him, but gosh did it feel like he was getting blame for this “I had to—!”

But he didn’t have time to explain.

Because Donnie’s eyes rolled back and his body slumped forward into Leo’s arms—still breathing, but trembling.

His brothers screamed in panic, crying out Donnie's name

And the lab lights throughout the lair flickered.

.

.

.

The lair hadn’t been this silent in months.

Even in the aftermath of the invasion, when their home was cracked and broken, there had been life.

Voices.

Hope.

But now?

There was only the sound of machines humming in Donnie’s lab. The dim flicker of purple-blue light. A monitor beeping, steady but eerie. And Donnie, unconscious, resting on the reinforced bed beneath a mystic stabilizer dome—his body lit with soft pulses from beneath the skin. Like his bloodstream was still charged with something electric. Something unnatural.

Something that didn’t belong.

Leo sat close by, knees tucked to his chest, eyes never leaving Donnie.

His eyes were red-rimmed and he was shaking slightly

He hadn't said a word since they'd brought him back in.

Leo really wanted to touch Donnie so badly and it was killing him inside that he couldn't. Couldn't comfort his twin in the way that he wanted to

Raph stood in the doorway with arms crossed, jaw tight. Mikey paced restlessly. April stood beside the med bay console, fidgeting with a loose thread on her jacket, her brow deeply furrowed.

And Draxum worked.

Rapidly. Silently. Methodically.

“Talk to us,” Raph finally said, voice sharp. “What is happening to him?”

Draxum didn’t turn. “The prototype compound triggered a secondary mutation.”

Leo flinched but didn’t interrupt, burying his face in his knees.

Draxum went on, tone clinical. “The Krang remnants in his system didn’t just resist the serum. They adapted to it. Interfaced with it. It didn’t just cure the cancer—it rebuilt part of his neural and cellular framework.”

April blinked. “Are you saying it rewired his brain?”

Draxum paused. “In a sense… yes.”

“That’s not a cure,” Mikey whispered. “That’s a transformation.”

Leo finally looked up. “Is he still Donnie?” and gosh did Leo's voice sound wreck

Thankfully, no one commented on it

Draxum turned to him, his expression unreadable. “Yes. But… altered. His intelligence, sensory input, and possibly even his perception of time and consciousness have changed. The echoes of the Krang tech are no longer just parasites—they’re part of him now.”

April stepped forward, voice tight. “Is he in danger?”

Draxum’s lips thinned. “He is the danger. If his powers expand without control—”

“Donnie wouldn’t hurt us,” Leo growled, standing up sharply.

The shift in tone and posture was swift and unexpected, though it made sense for the older twin. He was always protective of Donnie, ready to defend on his behalf

“I’m not saying he will,” Draxum said coolly. “I’m saying we can’t predict what he’ll become.”

As if on cue, the monitor beeped irregularly.

Donnie stirred.

Everyone froze.

Leo rushed to his side, gently placing a hand on his shoulder, feeling relief at being able to touch his twin but scared of what might happen. “Dee? I’m here.” he said softly. He didn't want Donnie to wake up alone and scared and he figured that his grounding touch would be enough

Donnie’s eyes blinked open. But this time, the glow was unmistakable—like tiny stars had been caught inside his pupils.

He looked up at Leo. “Your blood pressure is elevated.”

Leo blinked. “Uh… yeah. That makes sense.”

“I can feel the heartbeat of everyone in this room,” Donnie whispered as he look at everyone before turning back to Leo. He reached out with his hand and placed it on Leo's plastron, right around his chestplate “Yours is the loudest.”

Leo gently held Donnie's wrist as his thumb came over Donnie's pulse point

Raph took a step back. “Okay. That’s... new.”

Donnie’s gaze drifted past Leo, toward the lab wall. “The wires in that panel are overheating. They’ll blow in about ten minutes.”

Draxum checked a nearby console. His eyes widened slightly. “He’s correct.”

Mikey looked between them. “So… he’s like a walking scanner now?”

Donnie took his hand off of Leo's plastron and slowly sat up, swaying slightly. Leo immediately steadied him.

“I don’t know what I am,” Donnie murmured. “But I can feel things. Frequencies. Signals. Heat. I think I could map the entire lair with my eyes closed.”

April whispered, “Is it painful?”

Donnie hesitated.

“Yes,” he admitted. “But not in a way I can describe.”

Leo’s grip on his shoulder tightened. “You don’t have to explain. We’re right here.”

But Donnie didn’t seem to hear him.

His hands trembled. His eyes flicked to the lights above. “They’re too bright.”

Leo reached up without hesitation and dimmed them.

Donnie exhaled shakily. “Thanks.”

Later, when the others had left to give him space, Leo remained.

Donnie sat with his knees pulled close, arms wrapped around them, fingers still twitching from the new stimuli.

“I don’t feel sick anymore,” he said quietly.

Leo looked over. “That’s good.”

“But I don’t feel normal either.”

Leo lowered his gaze. “That's...not as good. But...I did expect that, even though I hate it with every fiber of my being as...” Leo looked at his younger twin and sighed heavily "...I hate seeing you like this" he finished with a whisper

Donnie looked at him then, a lone tear slipping down his face as he said in a small voice. “I’m scared.”

Leo moved closer, briefly touching foreheads with Donnie. “Me too.”

The twins pulled away from each other and sat in silence for a long time, side by side, their shoulders touching. The way they used to as kids when one of them had a nightmare. Or when the world felt too big.

Donnie turned his head slowly, eyes still dimly glowing. “You still see me… don’t you?”

Leo didn’t hesitate as he wrapped Donnie up in a side hug. He kissed the top of Donnie's head before bringing their foreheads together again, one hand coming up to rub soothing motions up and down Donnie's arm

“Always.”

And for the first time in days—despite everything unknown, everything terrifying—Donnie smiled.

A small, broken, real smile.

Chapter Text

It started with a buzz.

Subtle. Harmless. A ripple of static over Donnie’s fingertips as he stood in the corner of the lower-level marketplace with his brothers and April. A quick supply run for fresh ingredients—simple, routine, meant to help Donnie feel normal again. Just one trip outside the lair.

One breath of freedom.

The sun was diffused behind a misty veil of clouds. The streets were quiet. The world felt soft.

Until it didn’t.

Donnie froze mid-step.

He gripped the strap of his satchel so hard it creaked.

His pulse stuttered.

A hum—low, resonating—started in the base of his skull and echoed down his spine. People moved around him, chatting, haggling, walking.

But to Donnie, they sounded like sirens. Every footstep a bang, every syllable a roar. The neon signs blinked like explosions in his peripheral vision.

And then came the pain.

It stabbed behind his eyes.
His skin prickled like static.
His fingers sparked with raw mystic energy—wild and uncontrolled.

“Don?” Leo’s voice, gentle but worried, filtered through the noise. “You okay?”

Donnie gritted his teeth.

“Too loud,” he managed. “Too much—”

Mikey reached for him. “Hey, let’s get out of here, it’s fine—”

A spark lashed out from Donnie’s palm.

It struck a nearby lamppost, sending a pulse of violet energy up its frame. The bulb shattered. Glass rained down. Civilians gasped and backed away.

“Whoa—!” Mikey shielded a kid nearby. April grabbed Leo’s arm.

Donnie stumbled back. “No, no—”

More sparks ignited from his arms, wild tendrils of energy licking the air. The aura around him surged—pulsating, unstable. Lights nearby flickered. Car alarms went off in the distance.

“Everyone back!” Leo barked, pushing people behind him. “Donnie, it’s okay! Just breathe, look at me—!”

“I can’t—I can’t stop it—!” Donnie clutched at his head.

His eyes flared with bright violet light.

And then—

BOOM.

A wave of energy exploded outward from his body, a full-force pulse of mystic feedback. The street cracked. Windows shattered. Power lines sparked and snapped overhead. The force was too sudden, too violent.

Leo barely had time to react.

He turned to shield a family—

And the blast hit him full-on.

He was flung across the pavement, crashing into the side of a van with a sickening crunch.

“LEO!” Mikey screamed.

Time stopped.

Donnie stood in the middle of the devastation, violet energy still crackling along his arms. His breath came in ragged gasps, and his pupils were blown wide with horror.

His body shook. “No…”

April and Raph ran to Leo’s side. He was groaning, bleeding from a cut above his brow, one arm twisted at a wrong angle—but alive.

Barely.

“NO—!” Donnie’s voice cracked like glass.

His powers sputtered and sparked again, unstable.

Leo looked up from the ground, dazed, and forced himself to sit up—to reach.

“Donnie—” he coughed, pain in every word. “It’s okay—look at me, I’m okay.”

Donnie’s feet wouldn’t move.

The world felt miles away.

He had hurt Leo.

His twin.

His best friend

His Leo.

The one who stayed. The one who fought for him. The one who whispered reassurances in the dark and kissed his forehead like he was a person worth saving. A person worth loving

And he had hurt him.

Leo reached out again, eyes soft and full of unwavering love. “It wasn’t your fault. It was an accident, Dee. I know that.”

But Donnie couldn’t hear him over the roar in his own mind.
The guilt. The fear. The truth.

“I’m dangerous.” His voice was barely above a whisper, but Leo heard it. Those two words spoke volumes and it made Leo's heart shatter

“No,” Leo rasped. “You’re my brother. My twin”

Tears welled in Donnie’s glowing eyes.

“I—I can’t—”

He turned.

And ran.

“DONNIE—!”

But he didn’t stop.

He ran down the street, past the crowds, past the frightened eyes and broken glass and everything familiar, until the echo of Leo’s voice was nothing but a ghost in his ears.

And behind him, Leo lay in the arms of their family, bleeding, heartbroken, whispering his twin’s name into the wind all while tears flow down his face.

Chapter Text

The city swallowed him whole.

Donnie ran until his legs gave out.
Then he ran again.

Through alleyways and abandoned subway platforms, rooftops and shadowed back streets, guided only by instinct and the pounding terror in his chest.

His body pulsed with unstable mystic energy

Every step another spark

Every breath a storm.

He didn’t know where he was going.
He just knew he couldn’t go back.

By the time he collapsed in the far reaches of an old maintenance tunnel—deep beneath the city, damp and cold and echoing—his whole body was shaking.

Not from exertion.

But from guilt.

His hands were still glowing, pulsing faintly with that horrible energy. He stared at them, wide-eyed and breathless, watching as violet light crawled under his skin like veins of wildfire.

He could still hear the sound of the blast.
Still see Leo flying backward.
Still feel the moment everything shattered.

“I hurt him,” Donnie whispered into the dark, curling into himself. “I hurt Leo…I hurt my own twin”

His twin’s face burned behind his eyes—cut, bloodied, stunned but still trying to reach him.

Even after everything.

Even after that.

Tears welled up and fell freely, hot and silent. “I’m a monster.”

The tunnel didn’t argue.

It just echoed with his breath.

The lair was in choas

Leo was conscious now, arm splinted, ribs wrapped, but every movement made him flinch. Still, he refused to stay down. He stood leaning against the med bay doorway, eyes locked on Draxum and the monitors like he could will a location into existence.

“No luck yet,” April reported, phone to her ear. “He’s completely off-grid. No phone. No signal. It’s like he vanished.”

“He didn’t vanish,” Leo said quietly. “He’s hiding.”

Raph paced furiously nearby. “He’s scared outta his mind, Leo. He thinks he could’ve killed you.”

Leo’s jaw tightened. “Because he thinks he’s dangerous.”

Mikey stood beside him, biting his nails. “Dude… he’s not wrong. That blast could’ve—”

“Donnie would never intentionally hurt me,” Leo snapped, sharper than he meant to.

Everyone went quiet.

Leo took a breath, trying to steady himself. “He needs us more than ever right now. And if he thinks he’s alone…”

“He’ll never come back,” April finished quietly.

Leo’s eyes dropped to the floor. “He already thinks he’s a burden. A broken machine. If we make him feel like he is—”

“He’s not,” Mikey said softly. “He’s just hurting.”

Leo nodded. “And we’re going to find him. All of us.”

Donnie didn’t move for hours.

He sat in silence beneath the city, cold seeping into his bones, surrounded by damp concrete and rusty pipes and the hum of electricity.

A familiar buzz in the back of his skull.

He was beginning to recognize it now—his powers weren’t just reacting to the world.

They were pulling from it. Feeding. Interfacing. The electric grid, the mystic currents, the energy of the city itself—it called to him. And somewhere deep inside, it terrified him.

Because if he couldn’t control it…
Who else would get hurt?

A sudden surge of panic hit him. A flicker of light burst from his palm and cracked a pipe beside him.

He scrambled back, gasping.

“Stay away from me.”

That’s what he wanted to scream.

He needed to stay away from his brothers. From everyone

But he wanted them to come.
He wanted Leo to come.

Donnie needed his twin. He wanted Leo to hold him and tell him that everything was going to be ok. That after everything, Leo still loved him

But, that wasn't going to happen

And that broke him more than anything.

He buried his face in his arms as more tears came to his eyes.

“I’m sorry,” he whispered to the empty tunnel. “I didn’t mean to.”

Back at the lair, Leo suited up against everyone’s protests.

“You’re not healed,” Raph said, arms folded.

“I don’t care.”

“You can barely walk straight,” April added.

“I’ll crawl if I have to.”

Draxum finally spoke. “You’re the only one who might reach him. But if his mutation surges again…”

“I’ll take the hit,” Leo said. “As long as I can hold him.”

Mikey gently tied Leo’s mask for him before cupping his face, wiping away a lone tear. “Then let’s bring him home.”

.

.

.

Leo followed the hum.

Not the hum of the subway tunnels, or the dim flickering lights, or even the electric buzz from the city's underbelly.

He followed Donnie’s hum.

It pulsed in the air like a barely-there thread—faint, mystic, erratic. But Leo could feel it, deep in his bones, like how one half of a coin knows the other. A tether stretched thin but still whole.

And Leo followed it into the dark.

His ribs ached with every step. His arm throbbed in its brace. But none of it mattered.

Not when he finally turned a corner and saw a familiar figure curled in the shadows, glowing faintly violet, shaking like a leaf in the wind.

“Donnie…”

Donnie jerked upright, whirling around, his whole body tense. His eyes glowed like twin stars, his skin faintly pulsing with unstable energy. A spark jumped from his hand to the concrete floor.

“Stay back,” he rasped.

Leo froze. “Hey. It’s okay. It’s me.”

“No—no, no, you shouldn’t be here—” Donnie backed away, almost slipping in the grime. “I told you—I told you I’m dangerous—”

Leo’s heart cracked.

“You’re not dangerous,” he said, slowly moving forward.

Donnie shook his head hard. “I hurt you, Leo! I could’ve killed you!”

“But you didn’t.”

“I threw you across the street!” Donnie screamed, tears burning in his voice. “You bled because of me! You broke your arm because of me!”

Leo swallowed hard. “And I would do it again, Dee. A thousand times, if it meant keeping you alive.”

That made Donnie stumble.

His glow flickered. His breathing hitched. But then—

It flared.

A fresh surge of panic surged through him. Sparks lit across his shoulders. Mystic energy spiraled up his arms in jagged bursts. His aura expanded like a storm cloud, thick and out of control.

“No, no—Leo, I can’t stop it—!”

Leo stepped closer. “You can. You just need—”

“STAY BACK!”

The energy burst outward—raw and bright.

Leo threw his arms wide and walked right into it.

The impact nearly knocked him down. His skin tingled, his muscles screamed, and his injured arm jolted with a painful flare. But he kept walking, step by step, into the storm.

Donnie stared at him in horror, tears falling now. “STOP—PLEASE—I’LL HURT YOU AGAIN—!”

Leo fell to his knees right in front of him. His breath caught.

And then—

Very softly.

He said, “Then hurt me.”

Donnie froze. “What…?”

Leo looked up at him, eyes full of tears and pain and love. “If hurting me is what it takes to bring you back—then hurt me. I’m not leaving you down here. Not again.”

The sparks around Donnie faltered.

“You’re my twin,” Leo whispered, voice cracking. “My other half. I don’t care how scared you are. I don’t care how dangerous you think you are. You’re Donnie. My Donnie. I love you. And I need you.”

Donnie clutched at his chest like it was splitting open.

Leo pressed forward. “You told me once all you wanted was for me to be happy and healthy—even if you didn’t make it. But I want you to live, Don. I want to grow old with you. I want to argue with you over blueprints and eat your disgusting nutrient bars and watch sci-fi marathons until we forget what day it is.”

“I’m scared, Leo!” Donnie cried. “I don’t know what’s happening to me!”

“I know,” Leo whispered. “I’m scared too. But I’m not going anywhere.”

The energy flared one last time—

And then collapsed inward.

Donnie’s body shuddered. The glow flickered… and dimmed. His knees buckled, and Leo caught him mid-fall, pulling him close, wrapping his good arm around his twin as tightly as he could.

Donnie clung to him, sobbing. “I didn’t mean to—”

“I know. I know.”

Leo buried his face in Donnie’s shoulder, the two of them shaking in each other’s arms.

“You’re okay,” Leo murmured again and again. “I’ve got you. You’re safe. You’re not alone. I'm here. I'm right here Tello”

Donnie cried harder at the childhood nickname. "I love you Nardo. I love you so much"

Leo shed his own tears as he placed a kiss on the side of Donnie's head "Love you too Don-Tron. Always...and forever"

The storm passed.

And all that remained in the quiet was the sound of twin heartbeats—finally syncing again.

Chapter Text

They came home slowly.

Leo helped Donnie walk the last few blocks, even when Donnie kept murmuring that he could manage on his own.

Leo didn’t care.

He wasn’t letting go.

Not now.
Not yet.

Probably not ever again

By the time they stepped back into the lair, the quiet hum of home wrapped around them like a warm blanket. But tension still clung to the air like dust.

Raph stood up from the couch the second he saw them. Mikey and April rose too, cautious but visibly relieved. Draxum was already approaching, scanners in hand, expression unreadable.

But Leo held out a hand.

“Not yet.”

Donnie glanced up at him. And then past him—to the family he’d run from. The family he thought he couldn’t be part of anymore.

His throat tightened.

“I’m… sorry,” he said, voice raw.

Raph stepped forward first. “We were scared for you, Don.”

Mikey nodded. “But we’re glad you’re back.”

April gave him a soft, tight smile. “You don’t have to apologize for being scared.”

Donnie swallowed thickly, trying to steady his breathing as Leo guided him to sit. He kept expecting them to flinch, to pull away. But no one did.

Not even Draxum, who instead handed Donnie a warm cloth to wipe his face with before calmly beginning a scan—gentler this time.

“His mystic levels are high but stable,” Draxum murmured, mostly to himself. “Residual energy is self-regulating.”

“That’s good… right?” Mikey asked.

“Good enough for today,” Draxum answered.

Later, Leo sat with Donnie in their shared room, the glow of the nightlights bouncing gently across the walls. Donnie had barely let go of his twin since they returned.

“I’m still not okay,” he said softly, curled up in a hoodie two sizes too big.

“I know,” Leo said, sitting beside him, fingers tracing the hem of Donnie’s sleeve. “That’s okay.”

Donnie looked down at his hands. “It’s not just the powers. It’s me. I don’t know how to feel like myself anymore.”

Leo thought for a moment. Then nodded. “Then we’ll find you again. One piece at a time.”

Donnie looked over, eyes damp. “What if the old me never comes back?”

Leo’s voice was soft but steady. “Then I’ll fall in love with the new you.”

Donnie blinked, stunned silent.

Leo smirked lightly. “Not romantically, gross. We're brothers...twins after all. But you get it.”

A tiny laugh escaped Donnie’s lips.

Then, quietly, he leaned his head on Leo’s shoulder.

“Thanks Nardo.”

Leo leaned his head right on top of Donnie's, the two of them fitting together like a puzzle piece

Like they were always meant to be

“Always.”

The next few days were filled with adjustments.

Draxum and Donnie built mystic dampeners—bracelets that could ground Donnie’s energy when it flared up. Leo helped code safety protocols into them, while Mikey decorated one with glittery paint just to make him smile. Raph helped reinforce parts of the lair for safe testing. April brought calming oils and light therapy gadgets, and Splinter even taught Donnie how to meditate.

They set schedules.

Built routines.

Made space for Donnie to fall apart safely.

They recalibrated.

Together.

One night, Leo caught Donnie standing alone on a rooftop, watching the stars flicker above the skyline.

“Can’t sleep?” Leo asked.

Donnie shrugged. “My mind’s loud.”

Leo joined him. “Wanna talk it down?”

Donnie thought about it.

Then nodded. “Yeah. But only if you stay.”

Leo didn’t hesitate as he reached out to grab Donnie's hand.

“I’m not going anywhere.”

.

.

.

There was a whiteboard again.

Messy, crowded, covered in scribbled formulas and hastily sketched diagrams. The smell of soldering flux clung to the air, faint under the lavender oils April had insisted on using in the lab now. Two mismatched chairs sat side by side, and the room hummed with low energy—soft, steady, normal.

Donnie stood in the center of it all.

Hands on his hips. Hoodie sleeves rolled up. Mystic dampener fitted snug around one wrist. A stylus behind one ear.

“Okay,” he said, to no one in particular. “I’m ready.”

Small steps, Draxum had said.

So Donnie started with a test.

Not of power—but of control.

He set up a machine to measure the pulses of mystic energy he could generate now. A crude feedback loop of his own design, one that only he could calibrate. Leo sat nearby, half-watching, half-dozing, content to simply be in the room.

When Donnie channeled a pulse into the feedback terminal, it lit up—clean, contained, almost elegant.

Leo opened one eye. “That looked stable.”

Donnie smirked faintly. “It was. Better than yesterday’s.”

He didn’t say it out loud, but Leo saw it in his posture—pride. Quiet. Earned.

And for once, Leo let the tension in his shoulders drop.

That afternoon, Donnie worked with Mikey on helping power a hydroponic garden they'd been growing in one of the tunnels. Mikey was cautious at first, but when Donnie joked about it—“Worst-case scenario, I turn your lettuce into sentient vine monsters”—the ice broke.

They worked for hours.

Donnie didn’t spark once.

That night, he fell asleep on the couch.

Leo found him there, curled up with a notebook on his chest, and carefully draped a blanket over him. For a long moment, he just stood and watched—his baby twin, breathing softly and peaceful. But most importantly...he was here.

And something inside Leo finally cracked.

The exhaustion he’d been ignoring.
The fear he hadn’t faced.
The grief he had been holding at bay for weeks.

Because even with Donnie back, Leo hadn’t stopped bracing for another fall.

The next morning, Leo didn’t get up with the sun.
Didn’t rush to the med bay.
Didn’t check the dampener data.

He let himself sleep.

Donnie found him later, curled up in bed, hoodie stolen from his laundry basket wrapped around him like armor.

For once, Leo looked small.

Donnie didn’t say anything.

He just sat down beside him.

Leo stirred a little but didn’t open his eyes. “Can’t believe I’m the one oversleeping.”

Donnie gave a soft smile. “It’s about time.”

Leo cracked one eye open. “You okay?”

“Not completely,” Donnie said honestly. “But I’m getting better.”

Leo smiled at that, small and sincere.

“Good.”

They sat in the quiet, the twin rhythm of breath between them steady and grounding.

“You know,” Donnie murmured, “when I thought I might die, all I could think about was how I didn’t want you to carry that weight. I didn’t want to be your reason to fall apart.”

Leo looked at him.

And said, “You never were. You’re the reason I kept it together.”

Donnie smirked "Same here"

A silence passed between them. Not heavy—just full.

Donnie exhaled. “We’re a weird pair.”

“Best kind,” Leo replied, and nudged his shoulder.

Over the next few days, Donnie began tinkering again—really tinkering.

He wrote new code. Built updated sensors. Started experimenting with what he could feel through his secondary mutation rather than just fearing it. He and Draxum bickered constantly over protocols, and April filmed half of it with a grin.

The family began smiling more.

The air felt lighter.

Donnie started keeping a new notebook.

He titled it: Heartcode.

The first page simply read: Find what keeps you grounded—and keep programming toward it.

At the bottom of the page, Leo had scribbled in his own handwriting:

You. Always you.

Chapter Text

The mission was simple.

A rogue mystic pulse had been detected in the old subway lines beneath Midtown. Reports hinted it was leftover Krang tech—corrupted, unstable, and spreading energy spikes in unpredictable patterns.

April had traced the epicenter.

Draxum confirmed it was mutating the environment.

But it was Donnie who said:

“I need to be the one to go.”

The room went quiet when he said it.

Leo straightened where he sat on the med table, fully healed but visibly tense. “Dee…”

Donnie stood firm. Calm. No wild aura. No shaking hands. Just clarity.

“This thing is mystic-tech hybrid. That makes it mine to fix.”

Raph frowned. “You don’t have to prove anything, little bro.”

“I’m not trying to prove anything,” Donnie said softly. “I’m trying to finish something. For me.”

Mikey tilted his head. “You sure you’re ready?”

“No,” Donnie admitted. “But I’ll never know if I don’t try.”

His gaze flicked to Leo.

And that’s when Leo understood.

This wasn’t about control anymore.

This was about trust.

Leo stood up and walked to him.

For a moment, he said nothing. Then, very quietly, “Do you want me to go with you?”

Donnie blinked.

“I mean,” Leo added quickly, rubbing the back of his neck, “I’ll come if you want. But if you want to do this alone—if you need to—then I’ll stay.”

Donnie swallowed thickly. “I want you there. But I want you to trust me to lead.”

Leo held his gaze. “Always.”

The tunnels were worse than expected.

Wires hung like vines, pulsing violet. The walls twisted and groaned as the energy warped them. Leo kept to Donnie’s right, hands hovering near his swords, just in case.

But Donnie didn’t hesitate.

He held up a new scanner—something he’d built just the day before—and moved forward. “It’s feeding on a mix of mystic frequency and Krang residue,” he explained, eyes scanning. “We’ll need to isolate the pulse node and reverse the polarity.”

Leo smirked. “You sound like your old self.”

“I feel like a new one,” Donnie murmured.

They found the node at the heart of the tangle—a glowing core, twitching and throbbing like a second heart. It hissed when Donnie approached.

The energy flared—testing him. Threatening.

Leo stepped forward—but Donnie held up a hand. “I’ve got this.”

Leo froze.

And let go.

Leo wished that he haven't

Leo had believed him.

Because for the first time in months, Donnie had felt like himself—not cured, not perfect, but whole. Mystic energy glowing steady under his skin. Fear no longer controlling him.

They faced the node side by side.

It fought back harder than expected.

The feedback loop overloaded. Violet light exploded outward, spiraling in erratic, fractal bursts. Leo had shouted something, tried to shield Donnie—

But the blast turned on him.

He barely had time to gasp before the corrupted tendrils of energy struck straight for his chest, mystic venom aimed to pierce his heart.

And then—

Donnie moved.

Lightning-fast.

Shoving Leo aside.

Taking the hit head-on.

The sound it made wasn’t explosive—it was hollow. A quiet, gutting crack, like glass under pressure.

Leo hit the ground, gasping. Dazed. The stench of scorched energy thick in his nose.

Then he looked up.

And everything froze.

Donnie was still standing—

—but only just barely.

His eyes were wide, breath caught in his throat, body already trembling. Violet light poured out from a jagged rupture down his chest, spilling like smoke. His knees buckled.

“Donnie—” Leo scrambled toward him, heart crashing in his chest. “Nonononono—Donnie—!”

Donnie collapsed into his arms.

The energy inside Donnie was dimming.

Flickering.

Fading.

Donnie was fading

Leo crouched beside him, cradling him like something sacred.

Something precious. 

Leo's hands shook as he cupped one of Donnie's cheeks. “You saved me—why did you do that?! We were supposed to finish this together!”

Donnie smiled, weak but real. “Guess I still had one more heroic act in me…”

“Shut up,” Leo choked out, sobbing. “Don’t say that—don’t say it like you’re leaving—!”

“I don’t have much time,” Donnie said, barely a whisper. “Body’s failing. Too much energy loss…”

Leo clutched him tighter. “No. No, you’re not going anywhere. I’m getting us out of here—I can portal—”

Donnie weakly raised a hand, laying it over Leo’s.

“I can’t make the trip,” he murmured. “I barely have enough strength left to hold onto you.”

Leo’s vision blurred. “Please—don’t leave me Don—please—” Leo stammered as he tried to keep his younger twin close to him, clutching him with all that he had "I...I just got you back. You were healed. You were finally ok. You...you can't leave me Tello. Y-you can't" 

The tears came hot and fast down Leo's face as he stared into the fading light of his twin's eyes. The same eyes as him. The eyes that once held so much light, now fading. The only thing that remained was the undeniable love that shine through as Donnie's eyes tried to memorize Leo's face in his final moments

Donnie’s hand gently cupped Leo’s cheek. His thumb brushed along Leo’s red markings with all the tenderness in the world.

His gaze was glassy, but soft. “Leo… none of this is your fault.”

“But—”

“No,” Donnie said firmly, using every ounce of his fading breath. “You gave me time. You gave me a chance to live. The serum, the care, the love… it let me beat the cancer. It let me come home. I got to laugh with Mikey again. Argue with Raph. Build with Draxum. I got to be your twin again.”

Leo’s heart shattered. His whole body was shaking. “I can’t lose you. Donnie, I can’t—not now. Not like this. Please...”

Donnie exhaled slowly, chest barely rising.

His hand moved, fumbling at the back of his shell.

He pulled free a small, smooth black cube—a containment unit Leo recognized from Donnie’s battle shell. Inside, a fragment of soft violet energy pulsed.

Donnie pressed it into Leo’s palm.

“Give it to Draxum and Mikey,” he whispered. “They’ll know what to do.”

Leo stared at the cube in his hand, confused, desperate. “What is it…?”

“Part of my ninpo,” Donnie murmured, eyes fluttering shut. “A piece of me. My energy core so to speak. Not enough to revive me… not yet… but maybe one day…”

“Don’t talk like that—please—just stay. I-I need you Dee” Leo sobbed, holding his twin like he could shield him from death itself.

Donnie opened his eyes one more time. “I love you, Nardo. Always and forever. Thanks for taking care of me and for being the best twin ever”

Leo clutched him close, forehead against his. “I love you, too Tello. More than anything. You’re my other half. You’re my heart. My...my baby twin forever”

Their final moments were filled with silence.

Leo pressed a long kiss to the top of Donnie's forehead as tears continue to roll down his face. He cradled Donnie in his arms, rocking them back and forth and humming a soft lullaby from their childhood, wanting to make Donnie as comfortable as possible in his final moments

A soft smile lingered on Donnie’s lips.

Then the glow faded.
The energy stilled.
And Donnie’s body… vanished.

Leo remained frozen, arms wrapped around the space where his twin had been.

He let out a heartbreaking scream as he felt the other half of his soul being ripped away. No longer feeling the violet energy beside him or the warmth that normally came from his younger twin

The blue flame called out but the purple pixels did not respond as they were simply...gone. Erased from existence like they were never there in the first place

He stayed like that for a long time.
Eyes shut.
Tears falling.

Heart completely broken

For a while, the only thing that Leo could feel was agnoizing pain and heartbreak

Then...the numbness set in as reality crashed around him. A reality that no longer had his twin in it

Leo wasn't sure which was worst...the numbness or the pain/heartbreak

Leo determined both were horrible and it just made him want to lay down somewhere and just wither away. Follow his twin into death so that they could be together again

There was no life...no point of living if Donnie was right there by his side

But then...Leo remembered what Donnie had told him

Slowly, Leo opened his palm.

The cube still pulsed.

Weak.
But alive.

Which meant that Donnie wasn't truly dead

He was just in some in-between state so to speak

Leo could bring him back

When Leo finally stood, his body shook. His breath was ragged. But his eyes burned with purpose, determination and a love that was only reserved for his baby twin

He opened a portal with trembling hands.

And stepped through.

Donnie had saved his life.

Now Leo would save his soul.

He would bring his twin home.

No matter how long it took.

Chapter Text

The portal hissed open in the middle of the lair.

Leo stumbled through it.

Covered in dust, eyes red and swollen, fingers clenched so tightly around the small energy cube that his knuckles had gone white. The mission gear hung off him like it no longer fit. His bandana tails dragged behind him, damp with blood and tears.

The second they saw him, everyone surged forward

April, Raph, Mikey, and Splinter were at his side in a heartbeat

But Leo didn’t look up.
Didn’t speak.

He just stood there.

Empty.

“…Leo?” Mikey asked, voice quiet.

Raph stepped closer, eyes scanning the room behind him as if expecting another figure to follow. “Where’s Donnie?”

Leo’s lip trembled.

He shook his head once. A tiny, broken gesture.

And then he fell to his knees.

The cube hit the floor and rolled, faintly glowing.

Leo buried his face in his hands as his body began to shake—guttural sobs ripping free of him as the grief finally poured out. “I couldn’t save him,” he choked. “He saved me—but I couldn’t—he—he’s gone.”

April dropped beside him in seconds, arms around his shoulders. Mikey stood frozen, lips trembling, tears already sliding down his cheeks. Raph turned away for a moment, fists clenched, before slamming one against the wall and yelling out in anguish.

Splinter stood in stunned silence, his eyes wide with loss.

The family collapsed around Leo.

Together, they mourned the unthinkable.

The loss of their genius.
Their glue.
Their brother.
Their son.

Leo continued to mourn the lost of his younger twin, his eyes seeming to find new tears to shed

It took a long time for the sobs to slow.

For Leo to lift his head, eyes raw. He reached down with shaking fingers and picked up the cube again. “Donnie… he gave me this.”

Draxum, who had silently entered from the corridor, stepped forward. “What is it?”

Leo handed the cube over like it was a sacred artifact. “He told me to give it to you and Mikey. Said you’d know what to do.”

Draxum examined it carefully—eyes sharp, scanning, calculating. And then his brow furrowed in realization.

“…Of course he did.”

Everyone looked up.

“What do you mean?” April asked.

Draxum straightened, his tone steady, even in grief. “Donatello and I discussed this possibility a long time ago. Quietly. In case… the cancer ever took a turn. He designed this cube to store a stable echo of his mystic energy or ninpo, if you will. This was done in case the cancer took his life. Essentially, this is his consciousness

“You mean…” Mikey’s eyes widened. “That’s him?”

“His energy. His spark. Possibly his mind,” Draxum confirmed. “This is not a full resurrection. Not yet. But we had a contingency. A plan.”

Leo let out a breathless sound—a broken, half-laugh/half-sob as he wiped his eyes. “Of course he did. That’s such a Donnie thing to do…That's my younger twin for you”

April smiled through her tears. “He always prepared for the worst. But hoped for the best.”

Draxum’s gaze turned solemn. “To act on this… I’ll need to return to my old lab. Recover equipment. Begin rebuilding the regenesis pods—prototypes he and I designed to give form to preserved energy signatures. It will take time. Maybe weeks. Maybe months.”

Leo stood, fists clenched at his sides.

“I don’t care how long it takes.”

Raph nodded. “We’re doing this.”

Mikey’s voice shook, but he spoke clearly: “We’re bringing Donnie back.”

Splinter placed a hand over his chest. “No matter how long the path is. He is ours. We do not leave him behind.”

Draxum gave a single nod. “Then we begin tonight.”

The cube rested in the center of the worktable, glowing faintly—steady, pulsing.

Like a heartbeat waiting to return.

Leo stood by the table long after everyone else had gone to sleep.

He placed his hand beside the cube.

“I’m coming for you, Dee,” he whispered. “Just hold on.”

And from inside the cube, the light flickered—just slightly brighter, like it heard him.

Chapter Text

Draxum's lab was a mess of half-rebuilt machines, flickering cables, ancient Kraang tech, and mystic insulation threads Mikey helped weave with his powers. Draxum worked without rest, his coat tossed aside, sleeves rolled up, face grim with focus.

And Leo was there.

Every day.

Lifting, wiring, soldering, calibrating.
Reading Donnie’s old schematics.
Trying to decipher Donnie’s notes, even when the handwriting blurred from his tears.

But the deeper into the rebuild they got, the more complicated it became.

Stabilizers failed to align.
Mystic containment cores shorted.
The energy cube—Donnie’s heart, Leo called it—was dimming. Not in power, but in coherence.

“We’re pushing too fast,” Draxum warned. “If we force synchronization without structure, the imprint will degrade.”

“We don’t have time to wait!” Leo snapped.

Everyone flinched.

Mikey stepped forward, holding a spool of shimmering wire. “Leo, I miss him too, but—”

“Do you think I don’t know that?!” Leo shouted. “I brought him back in pieces. I held him while he died. I watched his energy flicker out in my hands. I can’t wait calmly while his soul sits in a box!”

The silence that followed was thick and sharp.

Draxum finally said, quieter now, “You are not the only one grieving, Leonardo.”

Leo’s breath hitched.

He turned on his heel.

And left.

That night, Leo didn’t join his family for dinner. Said that he wasn't hungry. He honestly haven't really been able to eat since the day Donnie died in his arms

Leo didn’t even return to his room.

He curled up in Donnie’s instead.

The hoodie still smelled like him—cool metal, synthetic fabric, and lavender detergent. Leo wrapped himself in it like armor, arms around a pillow as he tucked his knees up to his chest.

The soft glow from Donnie’s nightlight cube lit the shelves of old inventions, sketches, projects half-finished and abandoned.

Leo stared at them, eyes burning.

“You’d know what to do,” he whispered hoarsely. “You’d tell me to stop freaking out. You’d roll your eyes and insult my stress responses. And then you’d fix everything. Because that was what you did. Even though I never said it, it was one of the many things that I loved about you and why I was always so dang proud of you”

His throat caught on a sob.

“I’m trying so hard to be okay, Donnie. But I’m not. You were the one who got me. You always knew what I meant—even when I didn’t know what I was feeling. You were the only one who ever saw me without me having to say anything.”

Tears spilled freely now.

“I want you back. Please… I need you.”

He cried until he couldn’t breathe.

Until the weight of exhaustion dragged him under.

That night, Leo dreamed.

It wasn’t vivid at first—just vague impressions of the lair, laughter, light. His family, smiling around the dinner table. A version of reality where Donnie never got sick, where everything was fine.

But as the dream shifted, he found himself back in the subway, in the aftermath.

Donnie’s hoodie in his arms.

But instead of silence, there was a sound.

Faint.

A static flicker.

Then—
“Leo…”

Leo’s eyes flew open in the dream.

He turned.

Nothing. Only shadows and faint violet sparks.

Then again—louder.

“Leo… help me…”

His heart stopped.

The dream pulsed.

The shadows stretched, and from the darkness bloomed soft, glitching light—like code unraveling.

And a shape—tall, slim, familiar—standing just out of reach.

Leo stepped forward, breath caught.

“…Donnie?”

The figure looked up.

“I’m still here.”

Leo’s eyes flew open in the real world.

He bolted upright in Donnie’s bed, drenched in sweat, hoodie clinging to his chest.

The nightlight pulsed faintly.

The cube on Donnie’s desk sparked—once.

Leo stumbled over to it, hands trembling, eyes wide. He stared at the cube, heart hammering in his chest.

“Donnie…?”

No reply.

But he knew what he heard.

Chapter Text

Leo hadn’t slept since the dream.

He couldn’t.

He’d spent the rest of the night pacing Donnie’s room, hoodie still wrapped tight around him, the cube that stored Donnie's energy was held tightly in his hand. Leo's eyes were scanning it over and over again.

Waiting for another spark.

Another flicker.

Another whisper.

But the cube remained stilled, almost like nothing happened.

It didn’t matter.

He knew what he’d heard.

The next morning, the lair was quiet—muted by a new kind of grief. Everyone had heard Leo’s outburst the day before. No one had pried. They all just… let him be.

He found them in the lab.

Mikey was sorting mystic components into bowls, humming softly under his breath. Draxum was at a console, configuring energy readings. April typed notes beside him.

Leo stood in the doorway, fingers white-knuckled on the cube.

“I heard him.”

They all looked up.

Draxum furrowed his brow. “Heard who?”

Leo stepped forward, voice cracking. “Donnie. In my dream. He called my name. He said, ‘I’m still here.’”

Silence.

April exchanged a glance with Draxum. Mikey sat frozen.

“You mean… like, a memory?” April asked gently.

“No,” Leo said firmly. “Not a memory. It wasn’t just a dream. It was him. It felt like a signal. Like he was trying to reach me through the cube.”

Draxum stood slowly, folding his arms. “The energy could be interacting with your subconscious. It’s not uncommon to—”

Leo shook his head violently. “No! I know my younger twin’s voice. Don’t do this. Don’t make this something it’s not. It was him.”

Mikey stood up.

Everyone turned to him.

The youngest brother looked between them, then moved toward Leo, his eyes wide and wet with something like belief.

“…Did it feel warm?” he asked softly.

Leo blinked. “What?”

“Donnie’s presence. Did it feel… like him? Like when he used to sit next to you in the middle of the night, not saying anything, but you knew he was there?”

Leo swallowed hard. His voice was barely a whisper. “Yeah. Just like that.”

Mikey’s lip trembled.

“I believe you.”

Leo’s chest hitched.

Because it wasn’t just belief. It was the understanding in Mikey’s voice. That same gentle warmth Donnie used to tease them both about—Mikey, the empath of the group. Mikey, who could feel people without needing words.

“I think…” Mikey started, voice shaking, “I think his soul’s anchored to you. You were...sorry you are his twin. His tether. If he’s reaching out, it’s through you.”

Leo collapsed into a chair, cradling the cube, wishing more then anything that it was his baby twin. He wanted to have Donnie cradled in his arms so badly that it hurt. “I just… I don’t know what to do.” his voice came out in a whisper and it sounded so broken and so lost

Like someone who was desperately searching for their other half but couldn't find it no matter how hard they tried

Mikey sat beside him and—like he’d done when they were younger—curled up next to his big brother. Just sat there. No pressure. No pushing.

Just quiet support.

“Maybe we don’t need to do anything right now,” Mikey said softly. “Maybe he’s just saying he’s okay. That he’s waiting. That he knows you haven’t given up on him.”

Leo rested his cheek against the top of Mikey’s head, tears silently falling.

He really did appreciate what Mikey was doing and while he loved the comfort from his baby brother, he still wished that it was Donnie that was curled next to him

In a perfect world, he would have both of his little brothers in his arms

In a perfect world, Donnie would never have gotten sick and Leo wouldn't have this huge hole in his heart where his other half should be

“I miss him so much, Mikey.”

“I know, big bro. I do too.”

They sat there for a long time, wrapped in silence and hoodie fabric and shared grief. Draxum and April didn’t interrupt.

And in the stillness, the cube pulsed—ever so faintly.

Warm and alive.

That night, Leo didn’t cry himself to sleep.

He lay in Donnie’s bed again, yes. But Mikey was curled on the other side. Leo wore the hoodie. Mikey left a candle glowing mystically in the corner.

And for the first time in weeks—

Leo dreamed peacefully.

A hum.
A spark.
A voice, faint but closer.

“I’m waiting, Leo.”

Chapter Text

Mikey sat cross-legged on the meditation mat in the center of Donnie’s room. The lights were dim, save for a soft mystic candle flickering with ethereal lavender flame. The energy cube sat on a small pillow between them, its soft violet pulses steady. Like a heartbeat...like a whisper.

Leo sat across from him, hood drawn over his face, Donnie’s hoodie sleeves tugged over trembling hands. He hadn’t said much, just nodded when Mikey asked if he wanted to try something.

Now, his legs were crossed in front of him, hands on his knees, the cube placed between them both like a sacred thread.

Mikey opened his eyes slowly and exhaled.

“All right,” he whispered. “I’m gonna try to reach him. But I need you to focus on him. Not just the energy—Donnie. Your memories. Your bond. Think about your younger twin.”

Leo nodded once, throat tight. “I never stop. Donnie is all I think about. Bringing him back is what keeps me going”

Mikey gave him a sad smile and closed his eyes again. “Then hold onto that. Hold onto that love and determination”

Mikey's mystic energy flared gently, ribbons of golden-orange light threading through the air like tendrils of smoke. He raised his hands slowly, cupping the flickering cube between his palms, not touching it—just hovering, just feeling.

Leo did as instructed.

He thought about the sound of Donnie’s laugh.
The way Donnie always muttered in binary when frustrated.
The way he used to lean against Leo without asking—just knowing he needed someone close.

He thought about their arguments, their synced battle formations, the secret twin glances that meant paragraphs of understanding.

He thought about that final moment in the subway.

Donnie’s voice—“I love you, Leonardo. Always.”

Leo’s heart clenched.

And then—

A ripple.

The candle flame surged.
The cube pulsed once—twice.

Mikey’s breath hitched.

Leo opened his eyes, startled.

The world around them shifted, softening—colors bleeding like ink in water. The room faded into a lavender-hued void, hazy and glowing.

And then—

They heard him.

“Leo…?”

Leo gasped.

“Donnie—!”

“Leo, it hurts…”

Suddenly Leo felt it.

It hit like a tidal wave—sharp pain, like electricity running along his nerves, like something frayed and raw being pulled tight.

Leo clutched at his chest. His breath caught. He could feel Donnie’s confusion, the ache of being disconnected, the cold of isolation wrapped around his consciousness like frostbite.

He saw flashes of what Donnie saw: darkness, static, incomplete thoughts spiraling through loops of memory.

“You’re not alone!” Leo cried out, voice cracking. “I’m here! I’m with you—!”

Donnie’s voice was weak, crackling, like a corrupted audio file. “You feel like home… but it hurts, Leo… I-I can’t stay long...”

Leo reached forward instinctively, fingers brushing the cube.

“I promise you,” he whispered, eyes blurring with tears, “I’ll get you out. I swear it, Dee. I’ll bring you back. No matter what it takes, no matter how long. Just hold on. Please, just—hold on.”

There was silence.

And then—

“…I love you, Leo.”

Leo’s heart stopped.

His next breath came out as a sob.

“I love you too,” he choked. “More than anything. You’re my baby twin. My other half. And I need you.”

“I know…”

The light surged—

—and the connection snapped.

Leo fell forward, gasping, his hands shaking where they hovered above the cube.

Mikey caught him with both arms, pulling him in close as Leo collapsed against his chest, body wracked with sobs.

“It was him,” Leo cried. “It was really him…”

“I know,” Mikey said softly, tears streaming down his own cheeks. “I felt it too.”

Leo clutched Donnie’s hoodie tighter.

“I have to bring him back. No...I need to bring him back. I won't accept anything else”

Mikey held Leo closer. "We will bring him back Leo. Together"

From across the room, the cube pulsed faintly, the candle’s glow rising to meet it.

The spark still lived.

And now it had heard Leo’s promise.

Chapter Text

As soon as they were able to, Leo and Mikey told Draxum about their dream connection with Donnie

When Draxum heard, he immediately got to work...leading to where they are now

The cube sat in the center of the lab, quietly pulsing.

Draxum stood over it, monitors casting violet shadows across his face, gloves glinting under the light as he worked. The energy cube, though deceptively small, was holding layers of encrypted mystic data—intricate, brilliant, and unmistakably Donatello.

Mikey sat nearby, tracing calming circles on the floor with his mystic aura. His eyes flickered between the cube and Leo, who sat hunched over a stool, hoodie sleeves pulled over his hands, eyes distant and bloodshot.

Leo hadn’t spoken since the dream connection two nights ago.

He barely slept. Barely ate.
Just sat near the cube like a knight guarding a sacred flame.

Like an older twin protecting his younger twin...his other half

Then suddenly—

BEEP.
BEEP.
BEEP.

Draxum’s screens lit up.

The cube surged, and the light changed—brighter, frantic, urgent.

Draxum's eyes narrowed. “There’s a message hidden in the pulse pattern.”

Mikey leaned forward. “Like… a countdown?”

Draxum adjusted the dial. “More like a warning.”

Leo finally stirred. “What kind of warning?”

Draxum worked quickly, fingers racing over controls. A slow decoding process began unraveling a mystic script from the cube’s core. The display flickered, crackled—then solidified into a blinking series of glyphs, overlayed with Donatello’s voice.

Static. Glitch.

Then—

“…If this message activates… it means my containment is destabilizing.”

Leo’s spine straightened.

“If not anchored to a physical form within a specified window, my energy will disintegrate—permanently.”

Mikey gasped. “No—no no no…”

Leo shot to his feet. “How long?!”

Draxum’s brow furrowed. He translated rapidly. “Based on the decay rate and the timestamp embedded in the core…” He exhaled. “We have six days.”

The room dropped into suffocating silence.

Six days.

Six days before Donatello’s soul—his essence—would fade completely.

Six days before Leo would lose his twin forever

Six days until Leo would be half of a whole and be a twin no longer

The thought of it was unfathomable

Leo turned to Draxum, voice hard and desperate. “Then what do we have to do to stop it?”

Draxum hesitated. “The regenesis pod isn’t ready. I’d planned for months of recalibration, structural testing—”

“We don’t have months!” Leo shouted. "We only have SIX days until Donnie is gone forever. Six days until I lose my twin forever"

“I know,” Draxum snapped back, uncharacteristically shaken. “But rushing the process could cause a collapse. If we fail—”

“If we fail, he dies anyway!” Leo’s voice cracked. He turned, running his hands down his face, then curling them into fists. “We can’t wait. Not anymore.”

Mikey moved to Leo’s side, placing a hand on Leo's shoulder. “I’ll help however I can. We’ll get him back, Leo. We have to.”

Leo glanced between them, pulse racing. “Tell me what you need.”

Draxum looked down at the screen again.

Donnie’s message still pulsed across the feed, and at the end, in a nearly inaudible whisper of static—

“Leo… if you’re hearing this… don’t wait. Trust your gut. Trust your heart. I believe in you. And...I love you”

Leo’s jaw trembled.

He reached out for the cube, holding it like it was the most precious thing in the world

That was what Donnie was. Something precious that he loved and cherish and wanted to hold forever

“I love you too Dee. I won’t let you fade,” he whispered, a tear streaking down his face as his forehead barely made contact with the cube.

Then louder—fierce, certain: “We’re starting now."

That night, the lair was alive with motion.

Cables snaked across the floor. Mystical stabilizers pulsed at the edges of a growing containment chamber. Mikey drew mystic runes by hand, focused and trembling but determined.

And Leo—eyes burning with love and fear—stood watch by the cube.

Six days.

That was all they had.

But if anyone was stubborn enough to fight fate itself for their little twin—it was Leonardo.

Chapter Text

Time was a weight pressing down on Leo’s chest.

Every hour that passed chipped away at the chances of bringing Donnie back. Every flicker of the cube, every glitch in the containment pod, every test that failed—it all whispered the same terrible thing:

Not enough. Not fast enough.

You won't be able to save him in time

You'll never see your precious twin again

So Leo pushed.

Harder then he ever had before.

He was bringing Donnie home and nothing or no one was going to stop him or get in his way

He was the first one up.
The last one to rest—if he rested at all.

He wired stabilizers until his fingers blistered.
He soldered mystic-conductive metals under Mikey’s guidance, even when his hands trembled.

He barked orders—tight, clipped. Not out of anger. It was more so out of desperation.

Raph, April, Splinter, Mikey, Draxum—they all moved with him. No one questioned it. Not really.

Because they all felt it.

The clock ticking.

Donnie fading.

But by day four, the exhaustion showed.

Leo’s movements grew jittery.
His eyes were bloodshot, glassy, even when focused.
He kept talking to the cube when no one was listening.

Then he collapsed during a recalibration.

Mikey caught him before he hit the floor.

“Leo!” Mikey’s hands glowed faintly with mystic warmth, instinctively sending calming energy through Leo’s system. “Hey—hey, you with me?”

Leo groaned, lifting a hand weakly. “’m fine…”

“You’re not fine,” Mikey said softly but firmly, easing him down to sit. “Leo, you’ve barely slept in four days.”

“I don’t have time to sleep,” Leo snapped, the raw emotion suddenly boiling up. “Donnie doesn’t have time!”

“I know,” Mikey said gently.

“No, you don’t!” Leo shouted, his voice cracking. “You’re not the one who saw him disappear! You didn’t feel his soul fading in your hands! You didn’t hear him whisper his last words!”

Mikey didn’t flinch. He just looked at Leo with wide, patient, aching eyes.

Leo broke.

He dropped to his knees, hands gripping his head as sobs ripped from his throat. “I just—I just want him back,” he whispered. “I miss him so much. Every second. Every breath. I can’t do this without him, Mikey…”

Mikey dropped beside him and wrapped both arms around his older brother.

Leo clung to him like a drowning man.

“I’m so scared,” Leo sobbed, face buried in Mikey’s shoulder. “What if I’m too late? What if I fail again?”

“You won’t,” Mikey whispered, holding him tight. “Because you’re not alone this time. We’re all helping. I’m here. And Donnie… he’s still here too. You felt him. He’s waiting. You know that he will always wait for us. Wait for you”

Leo shuddered. “But what if I burn out before we get there?”

Mikey pulled back slightly and cupped Leo’s face.

“Then Donnie would tell you to stop being an idiot and take a nap before you ruin the whole operation.”

Leo gave a breathless, tear-filled laugh.

“Sounds like him.”

“Exactly like him,” Mikey said with a soft smile. “And you know he wouldn’t want you to destroy yourself trying to save him.”

Leo nodded slowly, still trembling.

“I just…” His voice broke again. “I miss him so much, Mikey.”

“I know,” Mikey whispered, hugging him again. “Me too. So much. But we’ll get him back. Together.”

That night, Leo finally slept.

Mikey sat at the foot of Donnie’s bed as he watched Leo sleep. His heart ached as he saw Donnie's hoodie draped over Leo’s shoulders like a blanket, clutching it like a lifeline. The cube pulsed softly beside them, responding—almost comforting. Almost like he knew the pain that Leo was in

And Mikey whispered to the glowing light:

“He’s still fighting for you, Dee. Just hang on a little longer.”

Chapter Text

The lab buzzed with electricity.

The containment pod stood tall at the room’s center, its metallic frame wrapped in mystic carvings and braided cables. Four stabilizers pulsed gently at its corners, glowing violet-gold, humming with a heartbeat-like rhythm.

Draxum stood beside it, arms crossed, brow furrowed in contemplation.

Leo and Mikey approached slowly—both still tired, but steadier.

“Well?” Leo asked.

Draxum glanced back. “We’re almost there. The pod is operational, energy containment has stabilized, and the pulse converter is syncing to the cube’s resonance.”

Leo’s heart skipped. “So… we can bring him back?”

Draxum’s face tightened. “Not yet.”

The hope drained from Leo’s chest like a cracked pipe.

Mikey stepped in. “What’s missing?”

“The convergence matrix,” Draxum explained. “A neural-mystic translator Donatello designed himself. It bridges energy pattern to body, memory to brain. Without it, the pod can only house his energy, not reconstruct his mind.”

“So build one,” Leo said sharply.

“I’ve tried,” Draxum said. “But the schematics were incomplete. Donatello encoded the rest in his private drive—which was corrupted during the final transmission. I’ve exhausted every route I know.”

Leo’s jaw clenched.

They were so close. They can't stop now

Where could they get the design for the translator in a timely matter?

An idea then struck Leo

If Donnie was the one to designed it, then why not go into the brain of the genius himself?

He stared at the cube on the nearby table.

“…Then we ask him.”

Draxum’s head turned sharply. “Leonardo—”

“He’s in there,” Leo pressed. “We’ve already made contact. If we can stabilize another connection—pull the information from him—we don’t need the schematics.”

“That’s an immense risk,” Draxum warned. “The last contact was a brief tether. Reopening that kind of link might damage both your mind and the energy core.”

Mikey gently put a hand on Leo’s arm. “You don’t have to—”

“I do,” Leo said, eyes locked on the cube. He then slowly walked over to it and picked it up, holding it gently in his hands. Like it was something fragile “We’re running out of time" Leo spoke softly "I’m his tether, right? His anchor. His twin. If anyone can reach him—it’s me.”

Draxum was silent for a long moment.

Then: “I’ll prepare the psychic ring.”

A huge smile appeared on Leo's face

They were finally getting somewhere and they were one step closer to bringing his beloved twin back

They set up the connection in Donnie’s room—quiet, safe, familiar.

Mikey sat beside Leo again, hands glowing, ready to lend mystic support if needed.

Leo took a deep breath and gripped the cube tightly in both hands, holding it to his chest. Right where his heart was

“Okay, Dee…” he whispered. “I’m coming. Just...hold on little bro”

The room dimmed.

Mikey pressed his hand gently to Leo’s back.

And Leo’s mind fell into the connection.

At first, it was static.

Then pain—sharp, cold, distant.

Leo clenched his fists. “Donnie… come on. Come back to me…”

Through the void, flickering lights. Code unraveling. Memory fragments falling like shards.

Then—

A voice.

“…Nardo?”

Leo’s eyes filled with tears. “Tello—!”

He ran through the dreamscape toward the shape forming in the light—shimmering, ghostly, but whole enough to reach for.

Donnie’s figure flickered—but his eyes locked onto Leo.

“You came back.”

Leo grabbed his hand. “Of course I did. I always will.”

“…Why do you look so wrecked?”

Leo laughed through a sob. “Because you’re a pain in the shell and I love you more then anything else in the world. Because I miss you so much that it hurts and I’m trying to rebuild you with no instruction manual.”

Donnie’s smile was soft, flickering. “Sounds about right.”

Leo squeezed his hand. “We’re almost there, Dee. The pod’s built—but we’re missing the convergence matrix. The blueprint was in your drive—it’s gone.”

“I remember it.”

Leo’s heart leapt. “Can you show me?”

Donnie raised his hand—and a stream of glowing data flowed from his palm into Leo’s. Symbols, shapes, sequences—all instantly familiar.

Then Donnie’s figure faltered.

Leo immediately began to panic as he tried to keep his grip tight on Donnie

“No—stay with me—please Dee. I miss you so much. So please...stay” Leo begged his twin

“Leo,” Donnie said gently, as he cupped one of Leo's cheeks “I’m not strong enough to hold this form for long. But… I knew you’d come. That’s why I left the trail.”

Leo’s eyes burned as his hand came up to hold Donnie's hand on his cheek in place. “You always plan ahead.”

“Yeah,” Donnie said softly. “Especially for you.”

Tears ran down Leo’s face.

“I’m bringing you back, Donnie. I promise. And when I do… you’re gonna get so sick of hearing me say this, but I don’t care…”

Leo stepped forward, wrapping his arms around his twin’s flickering form, squeezing him as tightly as he could.

“I love you.”

There was silence.

Then Donnie’s arms returned the embrace.

The contact was barely there but it was enough for Leo

“…I love you too, Leo. I’ll see you soon.”

And with that—

Leo woke up.

He sat up sharply, breath catching, eyes wide. The cube was glowing bright and steady in his lap.

Mikey leaned forward. “Leo—?”

Leo turned to him with a shaky smile. “We’ve got the design.”