Archive of Our Own ^beta

Chapter Text

The first clue for Sherlock that today might be interesting was when he awoke and found he had turned into an otter.

Now, there are several ways to react to such a discovery, most of which would involve some variations of panic, frantically trying to wake up, or potentially plotting to murder your roommate for drugging you, but Sherlock, being Sherlock, mostly stared at his (tiny, furry) hands for a moment and then determinedly wriggled over to his nightstead.

Obviously, there was a very clear solution for all this.

xxx

It was a very tired and cranky half-dressed John Watson that stumbled into his bedroom some ten minutes later, clutching a cellphone and asking,

"Sherlock, care to explain why I received five texts from you at around six in the morning, all some sort of variation of, and I quote 'Require immediate assistance; am otter', Sher – Sherlock?“

John Watson paused. This was mostly he was now beholding the small aquatic mammal that was sitting on Sherlock's bed and holding a smartphone.

"Okay. No.“ John said very firmly.

xxx

The otter blinked at him. Somehow, it seemed to manage to look expectant and condescending at the same time, which really shouldn't work, mostly because the thing happened to be a bloody otter -

John managed to rein his runaway train of thought back in and pinched the bridge of his nose. It was too damn early for mind games.

"Okay, Sherlock, I am not playing along,“ he said, trying to remain calm. "I don't know where you're hiding, and I don't know what could possibly have motivated this latest exercise in insanity, but this is ridiculous, even for your standards. I'm going to go back to sleep. If this trained otter isn't back in the zoo or wherever you stole it from by midday, I'm going to tell Mrs Huds-“

"For goodness' sake, John, this isn't a trained otter, this is really me!"

John paused. And stared.

On the one hand, the otter had said something that sounded vaguely like "NUGNUGNUGNUG!“

But on the other hand, he had suddenly clearly heard...

"Did you just...speak?“ he croaked.

It had even sounded like Sherlock's voice – or like a voice would sound if it bypassed your ears entirely and ended up straight in your brain.

"Sherlock...is...is that actually you?“

The otter regarded him now with a slow blink and a look of that John thought would have been impossible to imitate.

Well.

In Sherlock's case it would have come from a bit higher up, not from somewhere around coffee table height, but...

"Yes, John, it is.“

"Okay, this is beyond weird. I can hear your...ottter noises, but also your voice and -“ John stopped himself and frowned. „Wait, again, this isn't you hiding somewhere and using cameras and microphones to spy on me, right?“ He turned a suspicious look on the small animal. "Sherlock, if you've managed to lace my tea with drugs again, I swear I'll-“

He broke off.

I am, he realized, having an argument with an otter. In my flat, at six in the morning.

"I need to go back to sleep. Maybe this really is just a horrible nightmare,“ John muttered, trying to head toward the door again, but paused when the otter gave a somehow frustrated-sounding squeak, that, again, just was entirely too familiar to John's ears despite everything. John heaved a very deep sigh and turned around again, crossing his arms.

"Okay. Prove it. Make the otter do something that only you could do.“

The furry creature regarded him from a moment with eyes that the longer he looked at them he couldn't deny were too intelligent for anything non-human. Then it (he?) all at once jumped down from the nightstead, scrabbled to the foot of the bed and then deftly worked its little claws into a narrow little slit between two floorboards, eventually flipping a little panel open that John never would have seen otherwise. The otter reached down and (with some fumbling) managed to retrieve a small, thin object. It took John a moment to process what he was seeing.

Then:

"Sherlock?“

"Yes?“

"Please tell me that this isn't a syringe kit loaded with...whatever Lestrade was looking for during the last drug bust.“

"It's not like I was ever planning on using it, John," the otter pointed out, doing something that looked oddly like a shrug.

"Yeah. No, of course not,“ John found himself saying, "You'd first have to calculate the new dosage for someone who has abruptly lost like 165 pounds, for one thing.“

The otter gave him a look that suggested he was not impressed with the comeback. Then:

"I wouldn't have to. The precise dosage for otters would be-“

"Oh god, of course you would know that,“ John groaned, rubbing his eyes. "Fine. Fine. Assuming this isn't a hallucination, what do we do now? How can you turn back to normal? How did you even turn into an animal in the first place?“

"I need to verify a few things at the lab.“ The otter lifted its tiny forelegs, looking up at John. "Carry me,“ it commanded imperiously.

John blinked. "What.“

"Don't be obtuse, John. Waddling about like this is far too tedious. My limbs are even more stubbly than yours now. I don't even seem to be a fully-grown otter, for one thing,“ the otter said, sounding displeased. 

A few minutes later, walking out of Sherlock's bedroom and trying not to fall down the starirs because he was utterly sleep-deprived and now had an otter on his shoulder, John Hamish Watson once again contemplated life choices, and where he had possibly made a few wrong ones.

To be continued...

Chapter Text

It was now about one and a half hours later and John was gradually feeling a little better, as long as he didn't remind himself that his flat mate was now a small aquatic mammal.

A previous line of questioning (“Why are you now an otter, Sherlock?” - “Can't say. Not enough data .” - “It shouldn't technically be possible for a human to turn into an otter. You...you do know that, right? It's an important rule, actually. Like the Earth going around the sun.” - “ Yes, John, thank you, I was aware. But clearly, we have been presented with evidence to the contrary for at least one of those facts. Do pay attention.”) had not resulted in John comprehending the situation any better.

Instead, Sherlock had directed him downstairs into the living room where he had jumped off John's shoulder onto the coffee table and then demanded that the laptop be opened for him. As soon as the browser had booted up, the otter had flung himself into research immediately, and then refused to communicate in anything but unhelpful grunting noises.

This, at least, was comfortingly familiar territory.

John had ambled back upstairs, and then took his own sweet time in the bathroom with a leisurely shower, guessing correctly that this was very likely the last down time he'd have for a while as soon as Sherlock had worked out a plan of action to rectify this current crisis.

This was proved correct as soon as he entered the living room again.

“Sherlock?” John asked. The otter didn't look up, small black eyes still narrowed at the now ridiculously huge screen in front of him, currently showing a newspaper article about a robbery. John, used to this behaviour as well, continued anyway. “Sherlock, I'll need to go out before we do anything. There's no food left-”

And this was as far as he got, because then he was already interrupted by a friendly, elderly voice going 'Yoo-hoo! Are you awake yet, Sherlock? It's only me, I came to drop off the keys and some food for you two, I'll be in and out in a flash.”

At the same time, the door to the living room was already opening, and for once, Sherlock and John both exchanged the same alarmed glance, because the otter on the chair was in plain view for anyone setting even one foot into the room.

“Hello, Mrs Hudson,” John said and then smoothly dropped the largest cushion they had onto his flatmate.

“John, dear!” Their landlady's face lit up as she saw him. “Up so early? You should really try to sleep in on a Saturday, dear, I know that living with Sherlock you need all the rest you can get.”

“You have no idea how right you are, Mrs Hudson.”

The old woman laughed. “I know, I know. Anyway, I will be gone until Thursday night so I brought you the extra key ring for the cellar and the attic and any food I still had in the fridge that would spoil-”

“Wait, what? You're leaving?” John managed, finally starting to figure out what had prompted this ill-timed early morning visit. He also tried ignore the cushion on the chair that now had started to bounce somewhat angrily.

Mrs Hudson nodded. “Yes. I told Sherlock that I would drop off the things today, but I can see he didn't mention it to you, and then he's of course out when I come.” Mrs Hudson shook her head and sighed. “Bigger fish to catch, I suppose.” She sighed, then saw John's face. “Did I say something funny?”

“What? No. Sorry,” John hurriedly schooled his features into an innocently friendly expression and then tried to usher her out of the door again. “Thank you very much for the food. You said you'd be back Thursday?”

“Yes, that's right, dear, just visiting my nephew for a few days. I hope you'll be alright by yourselves?”

“I really hope so too, Mrs Hudson,” John muttered.

“What was that?”

“Nothing at all. Have a nice few days!”

The door fell into the lock again with John collapsing against it like a man who had just fought off an invasion by the huns. Then, of course, there was another frustrated squeak from the sofa and John's eyes hurriedly flew open again.

“Oh god, Sherlock!”

John stormed over and lifted the pillow again. The face that greeted him somehow managed to look both crumpled and insulted.

“Really, John, was that necessary?” Sherlock asked a bit peevishly, but John didn't grace that one with a reply. Of course, with Sherlock as a tenant Mrs Hudson probably had seen weirder things than this, but even the eccentric detective generally didn't harbour livestock.

“It seemed safer,” was all John replied, letting himself drop into the other chair, while his flatmate weaseled over to the laptop again. “Anyway, found something out yet?”

“Not sure yet. I have found out I'm apparently an Aonyx cinereus, one of the smaller otter species. Also, somehow  only the size of a pre-adolescent pup."  The otter frowned.

"Hm-hm. Whatever it is must be acting on mental age, huh?" 

"Yes, John, thank you for that helpful comment. Also, I think you bent my whiskers.” Sherlock had just settled in front of the screen again, when a small alert noise announced to the world the arrival of an email. A tap on the touchpad called it to the full screen and John leaned over curiously.

“Something helpful?”

Black eyes roved over the contents quickly. “No, ” Sherlock replied dismissively. “ Just the Met stumped with a murder case so blindingly obvious even a child could solve it, as usual.”

“Even a pup?” John questioned, for some reason by now finding an odd sort of hilarity (probably born from despair) in the entire situation, but only earned himself a murderous glare from his flatmate. Sherlock gave the laptop a push toward John on the table.

“Here. You type. These digits are too short.”

“Yeah, you would make me type even if you had turned into a lemur instead.” John sighed and pulled the laptop over. The email consisted of a few short sentences, the problem apparently mainly that it seemed a locked-room mystery. The only window of the bathroom the victim had been murdered in was much too small even for a child to escape from. There were a few pictures of the crime scene, including the corpse, who seemed at first glance mostly unharmed even if their face was contorted. But...there was something strange about his hair...John started to lean forward, squinting at the picture, but Sherlock cleared his throat impatiently, which in his new form made the otter sound like a small vaccum cleaner.

“John. Concentrate. Typing.” He stood up on his hind legs, gesturing with one paw. “Tell them they need to look for a discarded syringe, which was obviously what the poison was administered with. They have worked out it was poisoning yet, right? Also, there should be claw marks at the door and they should do a full lab report since the victim was definitely a user, and if they examine the window frame they'll find-”

“Sherlock, hold on! I can't type that fast!”

“Oh for god's- give it here. I'll do it.”

“Fine. I'll fix breakfast, then, shall I?” John tiredly pushed the laptop back to the cranky otter, raising himself from his seat. Sherlock started typing almost immediately, small paws flying over the keys embarrassingly actually really quicker than John's attempts had been.

“Honestly, John, I'm missing opposable thumbs and I'm faster than you.”

“Oh, go build a dam somewhere, Sherlock.”

“Actually, that's beav-”

“I know! I'm a bit out of sorts today what with you being an otter, I'm sorry!”

It had been his first outburst, and now Sherlock actually looked at him for a moment, not saying anything. Then he glanced away and when he spoke, his voice sounded a lot less pompous and more sincere.

“...I understand.” He looked down at himself. “Bit of a shock myself, if I'm honest.”

John, who could recognize a peace offer when he saw one, sighed and tried a little smile again.

“Yeah, you can say that again. Hold on. I'll be out with breakfast in a mo.”

So saying, John stepped back into the kitchen where he pulled out the two slices of bread he'd put into the toaster sort of on autopilot previously, before another important question occurred to him.

What did otters eat?

xxx

It was another five minutes later that John stepped back into the living room. Judging by the ding! he'd heard while stacking the tray he was now carrying out to the coffee table, a new email had also arrived. An interesting one, apparently, because Sherlock had folded his paws under his chin now, staring at screen with slightly narrowed eyes. Watson knew that expression. It meant that if his flatmate had been a video game, there now would have been a loading bar.

“Here you go,” he said, putting something down next to laptop and otter. “I'm also going to mention that you used up all the milk without buying a new bottle again, and I'm half-tempted to tie a little purse around your neck and make you waddle to the nearest Tesco's. I'm serious.”

“Hmm,” Sherlock replied in that way he did that let John know he could have been talking about selling Sherlock to the London Zoo and he would be ignored, and he therefore just sighed once more and started on his own toast, waiting for the otter god to acknowledge him again.

He did when he finally looked up from the email and turned to inspect what John had put down next to him.

“John? You appear to have brought me a can of sardines.”

“Well, I don't know what otters eat. Fish, right?”

“John, these sardines are in tomato sauce.” The otter somehow raised an eye ridge. “Aren't you aware that it is generally ill-advised to give processed food to feral animals?”

“Well, excuse me for not researching the correct way to feed my flatmate while you were blocking the laptop with your otterfingers,” John grated, then became aware of how ridiculous their conversation was getting again and pinched the bridge of his nose. “Fine. I'll pick up some fresh fish. Have you any idea what we're supposed to do next?”

“I have a few ideas. Mainly I want to test the things I came into contact with yesterday for unusual substances, but for that we'll have to break into Bart's tonight. I doubt they'd let you in there with an animal.”

“Right.” John frowned. “So until then...”

“Until then, we'll be heading down to Lestrade's crime scene. He's replied to my first mail and what he wrote now definitely makes the case interesting.”

John stared at him.

“Sherlock. You're not serious.”

“It'll be fine. You can take your coat with the extra large pockets.”

“Sherlock!”

To be continued...

Chapter Text

It was a highly nervous John Watson approaching the crime scene that had been roped off in Belgrave Road, and the baby otter in his coat pocket didn't help any. 

“Where's the freak?” Sally greeted him at the tape line.  

“Uh...sick.” John rubbed the back of his neck self-consciously. “He...sent me. To tell him what I saw.”  

Sally did not seem to find his explanation very convincing, but, in the absence of any better alternatives, at least waved him through. John walked up the staircase that led toward the bathroom where the victim they’d seen the pictures of had died. Other officers were milling around in the house and John tried to see whether he could spot Lestrade. 

“If they find out I've brought a live animal to the crime scene, I 'll be lucky if they don't lock me up,” he hissed, aimed at his coat pocket. Sherlock wriggled and didn't deign that one with a reply. 

They had tried the trick with the laptop first, of course – this would have been so much easier if Sherlock could have stayed at the flat and John simply would have waved a computer with an open video call around the crime scene – but, as it turned out, the strange sort of 'telepathic connection' John seemed to have with Sherlock only worked in close physical proximity. As soon as he called the otter on a cell phone, all he heard was the weird NUG-ing. 

Which left John Watson in a murder room with an otter in his pocket. 

“If I were Bilbo and asked Gollum about what I have inside there, the Shire would be safe,” John grumbled. 

“What?” 

“Nothing.” 

“John? Where's Sherlock?” Lestrade greeted him as he entered the bathroom. Beside the Chief inspector, there were two more policemen in white overalls working on bagging evidence, and, of course, the murder victim, unclothed and sprawled ungracefully in the bath tub. 

“Sherlock's home sick. Turns out methodically starving yourself actually will compromise your immune system at some point – astonishing medical science, I know,” John replied glibly (ignoring the displeased snuff in his coat pocket at the comment.) “He asked me to come and tell him what I saw.” 

“Did he.” Lestrade didn't look too pleased with that.

“Yes, he did. And now get everybody out, I need to work.” 

It was a normal enough reply for Sherlock, John thought, the only problem being that this time, what everybody else in the room had heard- 

“What...what was that? Was there a noise from your pocket?” Lestrade asked promptly, staring at the bulge in the side of John’s coat that had already made him feel like London’s anatomically weirdest exhibitionist the entire time they were on the tube.  

“I, uh, I have a new ringtone?” John stammered, wishing he would die. In demonstration, he pulled out his cellphone from entirely the other side of his coat, and said “It’s uh, it’s a text from Sherlock. He says he, err, needs you all out of the room. He...doesn’t want you talking in the background when he calls. Yeah. Sorry,” John said, giving Lestrade the long-suffering lop-sided grin that he knew always made him look just a bit dopey; easy to trust or underestimate. It wasn't the most glamourous acting talent, but you worked with what you got. 

Lestrade gave him a look that seemed like the inspector was deciding whether it was worth it to enquire whatever was going on at the Holmes and Watson Residence of Madness this time and seemed to decide that no, this time it wasn’t. 

“...fine. Come on, guys, let’s take a short break. I trust you at least won’t steal or contaminate evidence like he usually does,” Lestrade said with a sigh (and another strange look at a haughty snuffle from John’s pocket) and shooed the other two officers out of the bathroom. Seeing as they were alone now, Sherlock poked out of the coat. 

“Very good. Lift me onto the rim of the bathtub.”

“Decided to return to your native habitat?”

“No. And in fact, the small-clawed Asian otter is the least aquatic kind of its species,” Sherlock replied irritably, “I want to get a closer look at the victim’s hair. ” 

“Yeah, I noticed it looks kinda weird, right?” John said, frowning as he also stared at the dead man in the bathtub, trying to figure out what bothered him about the hair. It probably said something about his life that staring at murdered corpses was now actually calming him down and seemed like a soothing activity in comparison. “Do you think-?”

“Sorry, John, but we’ll have to talk later. While your idea about a ringtone was quick thinking, for anyone listening, this many text messages would be suspicious, even for me.”  

“...sure,” John said weakly, choosing to sit down on the closed loo instead and then proceeded to watch his roommate scurry about the bathroom, occasionally getting up when Sherlock had fallen into the bathtub or had accidentally overturned a bucket onto himself. They did find the things Sherlock had suggested for the text - there was a syringe, as well as tiny clawmarks on the edges of the wooden windowframe and around the handle, as well as empty mug that Sherlock was interested in and asked John to steal from the crime scene for testing.  

And yet, the weirdest thing about this morning is probably still that he paid me a compliment , John thought with a sigh. 

xxx

“Okay, we’re back home. Now can you tell me what you’ve found or how you think you turned into an otter or, for that matter, if you’ve already figured out how you can turn back- ” 

“Not now, John. I need to send a couple of texts and I need you to get that mug of tea I drank from yesterday. No spilling the liquid inside. Put it in a container to carry and then we’re heading to Bart’s.”

“We’re heading to the sodding pound if you don’t knock off that attitude,” John muttered under his breath, but still searched their mess of a living room and kitchen to locate the requested mug. Sherlock, it seemed was at the laptop again and apparently engrossed at a notice of a break-in at a pharmacy now. 

“Very well.” Sherlock reached up to close the laptop. “ Let’s go.”  

“The game is a-paw, then?” 

“One more word, John.” 

xxx

“And are you absolutely sure there’s no one else in here today but us?” John asked wearily after they had arrived at Bart’s and he was now busy reaching for lab equipment from shelves far too high up for furry stubble fingers. “Also, me having to get things from high shelves for you ? You realize there is blackmail potential in this for a decade, right?”

“I may be an Asian small-clawed otter, John, but I am not at all averse to sink said appendages right into you, ” Sherlock replied, mental voice snappish. “ Also, set up the bunsen burner, will you? I tried and now am missing half my whiskers.”  

The otter now actually sounded despondent enough that John was half-moved to pity. “Fine, fine, just give me a minute. Also, would you finally mind explaining what we’re actually looking for and what on Earth your theory is for this frankly insane- ” 

“-John? I didn’t know you and Sherlock were coming in today, what - wait, is that an otter ?!”

Oh God. 

John turned around, half-frozen, staring at an equally flabberghasted Molly standing in the doorway. Next to him, Sherlock also appeared to be paralyzed from shock (but at least no longer holding a machine-printout in his front paws and very obviously reading it). 

“I - uh - I can explain -”

“Oh my God, it is ADORABLE!” 

John Hamish Watson did not see fear on his best friend’s face very often, but right now Sherlock was staring at the approaching lab technician with the exact same expression a real otter might have worn when faced with a hunting grizzly bear.  

“Er, um, Molly-” 

“Look at it, so TINY!” she cooed, already having bent down and was now wiggling a finger close to Sherlock’s snout. She looked up at John, smiling. “Does he bite?”

“Uhm. Maybe. If you keep doing that.” 

“Ooooh, shy, is he?” Molly looked at him with a still adoring expression. “What’s his name?”  

“Sher- uh. Sher...ry?” John suggested, not for the first time wishing he had been turned into an animal, so maybe Sherlock could have dealt with all this.   

“Sherry!” Molly exclaimed excitedly. “So it's a girl?!”  

“No. it's a...he. Um. Please don't turn him over to check,” John pleaded, “He, uh, is very shy,” he added, correctly interpreting the (now noticeably blanched) expression of the otter in question.     

“I wouldn’t!” Molly protested, “I mean, I love otters, I always used to visit them at the zoo as a kid, I never thought I’d get to…” she paused. “Wait. John. Why on Earth did you bring an otter to the lab ?” she asked, adoring joy replaced by frowning confusion in an instant as she seemed to become aware of their surroundings again. “You can’t do this! Did Sherlock make you do this?”  

“No, uh, I mean, yes, sort of - I’m here for an experiment. For Sherlock,” he tried to explain, aware that this day, somehow, was still managing to deteriorate.

“An...experi- with a live otter? He is making you experiment on live animals ? On endangered live animals?! ” Molly’s voice was now raised in indignancy, fury clearly just waiting to be unleashed -  

“No! No. Nonononono, Molly, I would never,” John interrupted her quickly, trying to stem the rising tide, “I even signed a petition in med school once, to stop animal testing. Really.” 

“Really,” Molly repeated skeptically, arms now crossed in front of her. “Then why, John, did you bring an animal to the lab?” 

“I, uh, it's just…” John racked his brain. “...he gets lonely.”

“...what?” 

Now both the otter and the woman were looking at John with pretty much identical expression, mostly suggesting that John may have inhaled a few too many experiment fumes.  

“Yeah, uh, it’s not my otter, see, I've got him only for a few days. From my sister,” John swallowed. “And it’s all legal, but...she said I mustn't leave him alone.  He… he gets depressed.”  

Once again, there was staring. John thought this wasn’t fair . 

“Well, that's what she said, anyway!” he added, more defensively now. “I just don’t want to have to lie to her when she asks me whether I’ve left Sherry alone, alright?!” 

“...oh,” Molly’s anger seemed to deflate a little. “Well, okay, that’s...that’s actually kind of sweet.” 

“ Thank you,” John replied with emphasis. 

“But this doesn’t change the fact that a live animal is completely against lab regulations and if you aren’t out of here in five minutes, I will report the both of you. And yes, I’m aware that Sherlock isn’t here right now but this is definitely his fault, somehow.” 

“You have no idea how right you are,” John muttered, but was at least glad that under Molly’s watchful glare, Sherlock didn’t put up as much of a fight as he could have. 

xxx

By the time they got back to the flat, it was already dark outside and John pretty much stumbled into the living room and tossed the otter-containing coat carelessly onto the couch, taking a small detour to the bathroom. 

“Okay,” he managed as he returned, “now that we’re alone can you please tell me-”

Which was a far as he got, because when he actually looked at his flatmate, Sherlock seemed to have crawled out of the coat, but then seemed to actually have curled up and fallen asleep in the bunched-up fabric. 

John looked at the tableau for another minute or two, took another blackmail picture, put out a fresh can of tuna, and went to bed. Maybe, just maybe, this would all go back to normal when he woke up.

At least, he thought as he locked the door to their flat, Sherlock in his current form probably couldn’t lockpick. 

To be continued...

Chapter Text

John's second day as a caretaker of his resident otter did not start out better than the first. 

There were a few, wonderfully relaxed moments in the beginning, where, indeed, John had woken up in his room, where everything was perfectly normal and sane, and he had lain there, almost having convinced himself that yesterday had to have been a horrible dream induced by some Sherlock-caused food poisoning, but - 

...then the toilet flushed and the bathroom door opened to a rather wet otter scurrying out of it and John groaned. 

Then his cellphone chimed, reminding him of the court date appointment that was today in two hours and John groaned again . 

Xxx

“What? No you can't possibly go to court today. I have a dozen errands I need you to run. Cancel. ” 

“Can- no, Sherlock, I can't bloody cancel a court date,” John was staring at the unperturbed otter incredulously, even if his now-aquatic flatmate was barely looking at him and seemed more interested in sending out another flurry of texts on his cellphone. Currently they were both seated at and on the breakfast table, even if Sherlock (predictably) hadn't even touched his can of tuna. 

“Of course you can. Just don't show up. They'll get the message.” 

“What they will do is suspend my licence,” John snapped back. “And I only have this appointment because of you! You needed to go chasing after this car, you refuse to ever learn to bloody drive yourself-!” 

There was a ring from John's pocket that cut him off, and it took all John had not to keep yelling at whomever unfortunate schmuck was at the other end of the line. 

“Yes?!” 

(Well. He tried, at least.) 

“Hello, am I talking to Mr. Sherlock Holmes? This is Emily from Diamond Pest Control services, just calling to inform you that a team of ours is en route to your location as requested and once again reminding you that the flat needs to be completely emptied out during the extermination. This includes both people and pets. The procedure shouldn't take longer than 8 hours until the flat can be safely entered again. Do you have any other questions at this time?” 

John took a very long breath. Then he used his absolutely most politest voice. 

“Ah, hi, Emily, thank you for calling. Actually, this is John, Sherlock's flatmate. Can you believe me my friend didn't even tell me you were coming today?” he let out a little ah-some-flatmates-right -laugh, that Emily reciprocated, but which at least had Sherlock blanching a little and retreating toward a hiding space behind the tea pot. 

“Yeah, uh, no, having the appointment today absolutely won't be a problem, especially considering that your next open spot, as you said, won't be for three weeks, right. So, uh, just one last question - what exactly did Sherlock call you in for today again? Oh, Brazilian army ants? Is that right!” John exclaimed as if in delighted surprise. “Well, thank you so much for calling, Emily, we'll be out of the flat in the next half an hour no worries. Ta!” 

John pressed the call away. 

The breakfast table appeared to be suspiciously empty of otter.

“Brazilian. Army. Ants.” 

“Well-” Sherlock did poke out from behind a stack of magazines now, “Technically, they're Chilean army ants which I now found out-” 

“SHERLOCK!” 

“They were for an experiment! They only escaped because I got distracted by the last case and-”

“I don't care! Sherlock! You're an otter and there's ants in the flat and now the exterminators are coming and I've got a court date-!” 

John broke himself off. 

“Oh god. The exterminators are coming and I've got a court date. You can't stay in the flat if they fumigate and I can't possibly take you to court, you have to go through security before you enter the building.”

“Well,” Sherlock seemed to try hard to keep his poise, swallowing with twitching whiskers. “I'd still suggest you don't go. Any difficulties that arise from you missing court, Mycroft can sort out-”

“Mycroft!” John exclaimed. “Believe me, Sherlock, the last thing I'd want is for your brother to get anywhere near this-!” 

“Oh, have I been expected?” 

John froze. 

Then, both him and the otter had absolutely identical expressions of existential horror as the door of the flat slowly opened, and a very familiar umbrella handle poked through. 

Xxx

“Well, well. I admit I never expect a particularly warm welcome, but this reaction seems a bit...overly dramatic?” Mycroft’s eye brows rose as he beheld John’s face as he stepped into the flat, murky blue gaze sweeping over the mess in barely veiled distaste. If he had noticed the (now frozen) otter half-crouched behind a stack of magazines, he gave no indication. “Tell me, John, where is my brother dear?” 

“Uh…” John frantically tried to get his vocal cords to work (and not shoot any suspicious glances towards any currently non-human residents in the flat). Mycroft meanwhile produced a black case containing several manila folders, seemed to look around for any non-horrifying surface to place it on and finally settled for holding it out to John. 

“I have some rather... unusual cases I want him to take a look at,” he said, giving a little sniff as John took the folder. The otter, unsurprisingly, chose that moment to sidle just a little bit closer, little beady black eyes now narrowed at brother and files. “Of course, due to their...slightly grotesque nature they’re still under wraps and it would be better for all concerned if they could be solved quickly before this reaches the public. Do make sure Sherlock takes care of them, will you?” 

“N-no,” John finally managed, “Listen, right now he can’t-” 

“Nonsense, of course he can. I can tell he is currently once more engaged in some sort of juvenile game of hide-and-seek, refusing to see me, but one hardly needs to take a look at the state of the flat and his...experiments to tell what state of mind he is in. Frankly, he should be grateful for this,” Mycroft said, lips just slightly quirked in an insufferable smile, and now John barely managed to grab the otter shooting forward, perhaps in an attempt to attack Mycroft’s ankle. 

“Sherl- I mean, Sherry, no!” 

“Unhand me, John!” 

“No, listen, you can’t-!” John broke himself off before it looked like he was actually talking to the clawing and hissing fur-sausage in his hands, Mycroft for once at least looking genuinely surprised. 

“A pet, John? A rather odd choice. Though since you inexplicably seem to like my brother and his temper I can see why you’d have gotten this one-” 

Which of course prompted another furious break for freedom from Sherlock, and John was sorely tempted to just fling the younger brother into the elder’s face. Only he then thought - 

“Okay, you know what? You. You take him.”

“I...beg your pardon?” Mycroft stared at John, with, curiously, the same expression of utter bafflement that was now also on Sherlock’s face (though in the latter’s case it was also now slowly turning to horror).  

“No objections,” John snapped. “Your brother bought this otter, and left me with it, and the exterminators are coming and I have an appointment I can’t take it to. You can search the flat for your sodding brother if you want to, but you take the otter for the day.” 

Mycroft continued to stare at him. The man could clearly tell John was lying, John knew, but fortunately, the truth was so insane that even Mycroft could not figure out about what he was lying. 

John took a deep breath. “If you do, I will do my best to get Sherlock to take a look at your cases. Okay? And you,” he added to the otter, “will behave, or else I will personally abandon you in a sanctuary, are we clear?” 

Mycroft once again only raised his eyebrows as Sherlock returned an absolutely withering look toward John, both of which John ignored.

“...fine,” Mycroft replied. “But I do hope my brother graces us with his presence before this day is over.” 

“Yeah,” John briefly pinched the skin above his nose. “So do I.” 

xxx

It was a little bit later in the day, Mycroft having long-since returned to his bureau, that he found he couldn’t stop looking at the animal.  

The otter - Sherry, John had said, though he had also said it was a male - had been placed in the only box available for transport in 221b, which happened to be an overly large, antique bird cage. Which was now sitting at the very edge of Mycroft’s very expansive writing desk, because John had specifically told him that the thing was apparently incredibly intelligent for its species and would escape if left unattended for even a minute. 

To be honest, part of why he had even agreed to this ludicrous request in the first place had been sheer curiosity why on earth Sherlock would have acquired an otter. 

Nevermind the fact that it was completely illegal, Mycroft was also a little bit baffled where he even would have gotten one - clearly his baby brother had been expanding his little net of strange contacts into the wild animal market. Even if this otter did appear to be somewhat of a...special specimen. 

Mycroft was almost inclined to believe John’s claims about its intelligence - after the animal had almost looked like it had sunken into an incredible sulk for the past few hours, only shooting what could not be called other than glares in Mycroft’s direction, for the last thirty minutes, once the papers spread all over his desk had started to push up against the bottom of its cage, it had actually begun to raise its head a little, small black eyes now apparently intently focused on the documents in its visual range, almost like it could really read - 

Mycroft briefly rubbed his face in his hands. He did need sleep. The nonsensical animal was starting to remind him almost of Sherlock with its posture and he could not be thinking about a single individual when the fate of states was on the line. He sighed, straightened the papers again and tried to busy himself with the documents again, trying to ignore the weirdly companionable feeling as if the otter was also reading along. 

To be continued...

Chapter Text

John stepped out of the building of Clerkenwell Court after only half an hour of humiliation while trying to explain how and why exactly he’d managed 13 different traffic violations within 15 minutes, though he actually thought the moment he’d dropped the name ‘Sherlock Holmes’, some of the expressions had indeed turned more sympathetic. 

Now it was back to Mycroft to collect Sherlock, although John by now was sorely tempted to retreat into a pub instead and relax for a few hours before the whole otter nonsense started again. With any luck Sherlock would not have bitten his older brother before he got back, nor escaped for the fjords. 

The ringing of his cellphone interrupted his dithering. John’s eyebrows rose as he saw Molly’s name on the display. 

“Hi Molly? Listen, I just wanted to say again I’m so sorry, if Sher-ry, uh, gnawed through anything or anything-”

“Hi John, no, I’m actually calling because - is Sherlock there?” 

“Uuuh, no, he’s currently...chasing some red herring, probably,” John said, voice admiringly steady. “Why?” 

“Oh damn,” Molly said. “Listen, we’ve just got the weirdest corpse in and now there’s - there was just some bloke in a suit, and I think they want to...red tape all over this. Like, we’re not allowed to do any post-mortem at all. I figured Sherlock might want to see it before they take it away, it’s honestly nuts.” 

“Okay?” 

“You’re sure he isn’t there?” 

“Pretty sure,” John said, “Though, tell you what, I’ll swing by. I’ll be able to at least give him a professional eyewitness account of the thing if I get there early enough before they take the body away.” 

“Alright,” Molly said. “But don’t bring Sherry again, okay? No matter if he gets lonely!” 

“Yeah, no, found him a sitter for today,” John grinned. “Be there in a bit.” 

xxx 

“Very well. I suppose it’s time for both you and me to have a spot of lunch, I suppose?” 

“Nugnugnug.”  

Mycroft raised his eyebrows. If he didn’t know any better, he would have said the otter’s reply had sounded sarcastic. 

Well. Not that he wouldn’t be deserving of some sarcasm, given that he had started talking to an animal. Mycroft pinched the bridge of his nose, trying to stave off a headache. The reports he’d been getting...it definitely was shaping up to be one of those days. 

But then again, the otter did seem to be kind of intelligent. Somehow. Mycroft stared at the otter with narrowed eyes, trying to figure out what it was about the animal that kept drawing his gaze back. Bizarrely, the otter held his stare, eyes now also narrowed and Mycroft briefly thought that if Anthea came in right now and caught him in a stare-down duel with an otter, he’d never live this down. 

“Alright. Nevermind. Stubborn little creature,” he muttered finally and leaned back, eyes closing for a moment. When he opened them again he tried to tell himself that the otter didn’t look triumphant. 

xxx

“So when you said, this is ‘nuts’...” John trailed off as he was standing next to Molly staring down at the corpse in the morgue. 

“Yes,” Molly said. 

xxx

 When John arrived later and was led into Mycroft’s office, he was surprised to find the large bird cage containing Sherlock perched just on the edge of his brother’s desk, and his flatmate curled up in it, fast asleep. 

“Ah, John,” Mycroft didn’t look up from his papers. “Has my brother had a look at the case files yet?” 

“Uh…” John eyed the documents on Mycroft’s desk. “You know what, it’s possible.” 

“Hmm. Do make sure he does, please. And I would appreciate being relieved of otter-sitting duties.” 

“Sure,” John said, stepping up to take the cage again. Inside, Sherlock appeared to be still out cold. “You...didn’t put anything in his food to make him sleep, right?” 

At that, Mycroft finally raised his head and then an eyebrow. “John, if irresponsible behaviour toward less intelligent creatures were my modus operandi, I wouldn’t be trying to run this country for the best of its citizens, now, would I?” he asked, lips once again drawn into the small sardonic smile that John suspected had so far at least caused half a dozen aneurysms in people having to deal with Mycroft. 

“Mycroft- ” 

“John. Calm yourself. I merely fed and petted him and he fell asleep.” 

“You... petted him.” 

“As a medical professional I’m sure you are aware of the stress-relieving properties of handling furry animals, yes? It’s biology, John. Much as my brother might believe otherwise, I do take my health seriously,” Mycroft said, already busying himself with his work again.

“Hm-hmm,” John nodded, tone just slightly higher-pitched than usual.   

“Anything else, John?”

Security footage of your office from the past several hours, please flashed through John’s head, but aloud he just said, “Nope! All good. I’ll get Sherlock to take a look at these cases, promise.” 

Sherlock thankfully continued to sleep through John’s journey home, meaning he could pretend to be a normal person who was carrying a giant bird cage with a blanket thrown over it on the Bakerloo line, and not a man who, judging by the noises, clearly had something other than a bird in there and was also arguing with it.

I will never, ever find a girlfriend, John thought not for the first time.  

xxx

“Evening, sleepyhead,” John said as he could hear noises of an otter stirring in the cage on the sofa table where he had deposited it, door wide open. “Enjoyed your stay with your brother?”

“If you should ever get turned into a hedgehog, John, I will leave you on the motorway.”  

“Charming as ever. Maybe remember which one of us can operate the can opener.”

“Irrelevant.” The otter made a paw gesture that was startlingly similar to one of Sherlock’s dismissive handwaves as he wriggled out of the cage. “Though I have at least managed to gather some interesting information during my...stay...at Mycroft’s office.”    

“Oh yeah?” John looked over from where he was busying himself with the kettle. The otter had gotten off the coffee table and was now rummaging in the box John had put Mycroft’s files in. At his question, Sherlock poked his head out, uprighting himself on his hind legs to be able to peer over the rim. 

“Yes. Like I suspected, I'm not the only one affected. There have been three strange deaths discovered so far, all of them leaving people...transformed. I suspect the one we saw at the crime scene yesterday may have only been the most recent victim.” 

John frowned, remembering the dead man in the bathtub yesterday. The one with the strange body hair patterns - which, if what Sherlock had said was true, then might have been fur ? 

“I….actually think I saw an earlier victim today, then,” John said. “Molly called me in, because, uh. They had a corpse in the morgue that was half-squirrel?” 

“Did she. I would assume one of you undoubtedly made an original pun of the nuciferous variety?” Sherlock raised an otterbrow and John declined to answer. 

“But nevermind. What we’re looking at is a medicinal trial, I suspect,” his flatmate scurried out of the box and onto the sofa again, curling into a thinking pose. “Someone has perfected a serum to induce an animal transformation. Only now they seem to be trying to concoct an antidote to it, but it’s not working as intended, instead leaving the people they’re trying to turn back half-transformed and dead.”

“Wait. You mean, someone is now intentionally transforming people into animals just so they can test their antidote on them?”

“Yes, John, do keep up. The break-ins at the pharmacies I’ve been looking into seem to match the pattern of ingredients such an antidote could be reasonably made from.”

John wanted to briefly point out, loudly and passionately, that there was no ‘reasonable’ in any of this case that involved people getting transformed into animals, but this didn’t seem like a very fruitful avenue to pursue. So he nodded. “Right.”   

“And judging by the state the victims have been found in, it seems like they’re getting closer to perfecting said antidote. Needless to say, we need to be there when they discover it.” 

“Of course,” John said, because this was his life now. “Do we have any idea yet what kind of serum triggers the transformation in the first place?”  

“No, since someone at Barts is inconveniently opposed against animal testing, even if it is the animal who does the testing,” Sherlock grumbled. “I had meant to do a blood test and some DNA sequencing for this very purpose before we were thrown out. But no matter. We can get the formula from the perpetrators when we have caught them. ” 

“Uh-huh. Any idea where we will catch them?” 

“...a few.” Sherlock scurried back onto the table and stretched himself on his hind legs to open the laptop again, turning it to John to show a map of London, zoomed in on Smithfield. “Judging from the area all murders and thefts were committed, it’s reasonable to assume that this is where they might also be using their lab. Or possibly even just a lab. ”

“Wouldn’t that be a bit risky on their part?” John asked. “They’d know they’ll get discovered far easier this way, wouldn’t they?”   

“Considering how hap-hazardly the last few murders were committed and the small claw marks at the door of the bathroom we surveyed yesterday…” the otter smirked. “I think something went wrong. I think they might be in desperate need of an antidote, too.” 

“Right,” John said. “So...we go looking for a lab now, or we’re waiting for another break-in or murder…?” 

Sherlock drummed his padded fingers on the laptop, frowning. “Hard to say. Without knowing whether they already have another transformed victim to experiment on, this is unfortunately a bit of a game of cat and-”

“Wait a moment. Hello, Molly?” John interrupted Sherlock, fishing his buzzing cellphone from his pocket and pressing ‘accept’ on the incoming call from their friend’s workplace number - which was strange, shouldn’t Molly already have finished her shift? 

The next moment, John’s heart sank as only a series of high-pitched squeaks rang from the phone, sounding like a mouse in severe panic. 

To be continued….

Chapter Text

Chapter 6: Animal Farm’s Got Nothing On This

John was sprinting towards the clinic’s doors, Sherlock scrambling out of his coat pocket and along his outstretched arm, punching in the key code he technically shouldn’t know and then hoisting himself onto John’s shoulder like the weirdest parrot in history as they slipped inside.

“I still think we should have alerted Lestrade,” John hissed under his breath, scanning the dark corridors of Bart’s, no evidence of anything out of order yet.

“And scare off our potential prey? No.”

“Your potential prey is herring.”

“Hush,” the otter shot back, and John did slow his steps as they descended the stairs towards the morgue and pathology lab, one hand hesitantly trying to feel for his gun tucked into the waistband of his trousers.

John froze as they saw the door leading to the lab standing just slightly open, a sliver of light falling into the corridor. As they listened, they could also hear the terrified squeaking coming from inside - and an ever so strange feral hissing.

“What the…?” John mouthed, the otter on his shoulder tensing his whiskers as he crept forward and tried to peer through the gap of the lab door…

And then stared, because inside, there seemed to be the weirdest game of not-cat and mouse going on he had ever seen in his life.

On one of the lab workbenches stood the familiar permanently installed large cooling unit, a small gap for ventilation underneath, just a few inches high - and which was now apparently the sole sanctuary of a single, panicked brown mouse underneath, who seemingly was alternately trying to make a call on the cellphone she had dragged under the thing with her, or attempting to make an escape from the white ferret carrying a syringe in its teeth that was currently darting around and around the fridge and trying to get at her.

“Squeak! Squeaksqueak-!”

“KchhChchchKCHCHch-!”

“What on god’s green earth,” John said, and then Sherlock screeched next to his ear and John barely had time to flinch away in reflex before pain exploded against the side of his head.

“ChhKchchh-?!” the ferret’s head had snapped up, little teeth bared in a snarl as it noticed the commotion when John cried out, blindly stumbling forward into the lab to get away from whatever had attacked him.

Sherlock was gone from his shoulder, fallen down or jumped off John couldn’t say, not while his vision was halfway blacked out from pain and his heart going in overdrive as he whirled around trying to face his assailant. The bright lights in the lab after the darkness in the corridor were blinding, his vision swimming with pain, but he could still make out a figure in the doorway; a tall white man who shut the lab door behind him and was now advancing, dressed in a beige suit - and more importantly, with a crowbar as an accessory - and already coming at him again.

“Kch! Ch-chhhCH-!”

Later on, John would blame his general dizziness for letting himself get distracted by a ferret, but fortunately, the man in the beige suit also turned -

“I know we need him alive, Jim!” he snapped at the small white animal while John tried to regain his bearings against a shelf, “If we didn’t, I’d have shot him, alright?!”

“Kchkchkch,” the ferret (“Jim”?!) commented dismissively, before again darting forward to cut off the escape route of the little mouse who had apparently just tried to sneak away to freedom while her captor had been distracted.

“Now, hold still and this won’t hurt a bit-” the tall, blond, would-be murderer said to John, advancing again and raising his weapon. John scrambled backwards, trying to scrabble for the gun in his waistband, only a small part of him wondering where Sherlock had gotten off to, hoping that the blow hadn’t struck him, and he was right now lying on the floor somewhere, bleeding or dead, little head with no chance to withstand the impact of a crowbar -

The other man lunged. John yelped, cursing himself for apparently forgetting all about fighting discipline at the first thought of having to take Sherlock to a pet crematorium, and barely managed to dodge the blow. The crowbar hit a pipe overhead instead, an old metal duct apparently connected to a boiler of some sort, because it broke under the blow and water started gushing out, splashing below onto the workbench and the embedded sink.

John had ducked under the swing and dashed through the spray and the splashes of water, trying to gain enough distance to draw his weapon and be out of immediate range of the crowbar. But the laboratory was just too small - there was a lab table in the middle, upon which some papers and an open suitcase with various chemicals, vials and syringes was lying, and a workbench running along all four walls around it, only interrupted by a gap for the door. The part of the bench directly opposite the door also had the cooling unit installed under which the mouse was still hiding, while another part - the one with the sink - was now partially underwater as the broken pipe overhead kept gushing, the sink already filling up fast.

And all it meant was that John could only keep running in circles around the table in the middle, there was no way he could open the door without the other reaching him and smashing his skull in, this time for good. And no time to reach for his gun -

A small brown shape shot across the floor and the split-second of distraction of the other man was John’s chance.

With a confidence in his knee holding up that he only ever felt when running alongside Sherlock Holmes, John kicked the large metal trash bin down in between the two of them and reached for his Glock.

And was too slow.

The attacker lunged and the crowbar came down on John’s hand hard, pain exploding as he could feel the gun getting smashed out of his grasp. John’s eyes widened as the weapon clattered to the floor, a howl of agony stuck in his throat as he saw the other man raising the crowbar again, ready to bring it down on John’s head this time. John was about to fling his arm up, knowing it would be his ulna shattered next, but unable to retreat or dodge in time -

And then the other man screamed.

Because an otter had just scurried up and rammed a very loaded syringe into his ankle - and as the man looked down, horror spread across his face.

“N-no!”

“Ch-KCCHHHH-!”

As John watched, wide-eyed (and the ferret...kcch’ed), his would-be assassin started to hunch over and howl, bones shifting in a way they were never supposed to, and then started shrinking (in a way physics should never allow to) and within a heartbeat, John wasn’t staring at a human man anymore.

But instead at the angriest juvenile honey badger he had ever seen.

It launched itself at him almost immediately.

“What-! What the-?! OW! You mangy-!”

“ROWR!” the badger commented in furious rage. Claws and teeth were swiping at John, uselessly trying to sink into arms fortunately protected by a thick leather jacket, John having successfully managed to catch the small beast in mid-air by its throat with his good hand, reflexes thankfully working where any higher brain functions had long since given up.

“Okay, you know what? This. This is where you go now,” John rasped, gritting his teeth in pain as he used his injured hand to grab the heavy metal bin, upright it and then tossed the yowling bundle of furry wrath inside it, slamming the lid on it again with satisfaction and holding it shut. Honey badger noises of apoplexy continued to issue from inside, but right now all John cared for was -

“Sherlock!”

His eyes roved through the laboratory, where was his flatmate, clearly Sherlock had somehow scurried up and then swiped one of the syringes from the lab table in the middle of the room before he attacked, but where was he now-?

“Give it up, Moriarty.”

“KchCHKch.”

John stared. Again. This was partly because Sherlock had just confirmed that the most dangerous criminal mastermind in the world was currently indeed an evil ferret, but also because the scene he was looking at right now could really not be looked at without staring.

Namely, Sherlock standing on his hind legs on the lab bench on the wall across the room from John, gaze focused on the white ferret three feet further down the bench, also upright - who was holding the syringe in one paw and one terrified mouse in the other.

“John has subdued your attack dog - or should I say badger - and there’s no snipers to save you this time. It’s over.”

As if he had also understood what Sherlock had been saying, the badger in question made another furious bid for freedom, ramming against the underside of the lid of the trash bin John was holding shut.

“Kch. Chh-hchkch. Kch-ch?” The ferret...asked(?), somehow, much like Sherlock, managing to sound entertained and haughty while being only a footlong, and then pressed the tip of the syringe’s needle against the mouse’s neck, whiskers twitching in cruel amusement.

“Squeak!”

To be continued...

Chapter Text

“Let her go.” Facing Moriarty with Molly still helpless in his grasp, Sherlock’s mind-voice had dropped into its most serious register, somehow still sounding as deep as always, even with the resonance body of a ribcage that could maybe hold half a cup of yoghurt on a good day.

“Kchht. Cht-cht-cht?” The ferret asked, challenge in its chittering.

“Then John will make sure your...companion…” Sherlock let the word hang in the air, “will suffer the same fate. John, grab the second drawn-up syringe from the suitcase, would you.”

The badger in the bin suddenly became noticeably more quiet, further proving that somehow, mice, otters and their assorted woodland friends all could communicate effortlessly here, even while their exasperated human ‘companions’ apparently, could only understand one of them each. The ferret’s eyes narrowed at the otter.

“Kch-ch’t.”

“He would.”

John reacted to the exchange by leaning over and grabbing the other filled syringe as directed from the table in the middle of the room, all the while not taking the other one of his hands off the badger bin. He wasn’t completely sure what was going on yet, but he knew a dare when he heard one and therefore also gave the ferret a defiant glare.

“And besides,” the otter made a movement as if he wanted to put his little paws into pockets of a coat he wasn’t wearing, realized this, and then tried to cross his forearms instead (but they were too short), so he ended up just putting them somewhere above his hips in exasperation, “you’re not sure what the serum will do, are you? No,” Sherlock said, looking as if he wanted to pace dramatically but was missing about three feet of legs to do so. Nevertheless, Moriarty watched him with uncanny attention, his fixation on Sherlock as unsettling as it had been when both of them had been bipedal.

“This is your latest version of your antidote, but you don’t know if it will turn a transformed person back into a human or kill them. Hence your need to transform Ms Hooper,” Sherlock continued, and while he still wasn’t pacing, his tail had started thumping a little, which John already knew was blackmail material for about a century if they made it out of this alive.

“She wasn’t just in the wrong place at the wrong time when you commandeered the laboratory. She was meant to be your latest test subject,” Sherlock said, starting to slowly close in on Moriarty, some changes in his body language now a reminder that otters were indeed still hunters. The mouse made a little whimpery sound.

“Which means that if you inject her now, either you kill her or you give her back her human form. And whichever fate it is, your hired help will share it - except, since he can understand you, he is not just your hired help, is he?” Sherlock asked, cocking his head. The amused expression had largely vanished from the ferret’s face, Moriarty now baring his little pointy teeth instead.

“No. But that doesn’t matter,” Sherlock said. “Because you don’t really want to inject her. You want to inject me,” he stated and the ferret’s tail twitched traitorously. The otter gave a little ottersmirk in triumph. “Not your first plan, probably - I suspect capturing and keeping me as a pet was in there, somewhere, when you managed to make John bring back that laced tea,” he continued, and John had a sudden, cold flashback to an incident two weeks ago, a man running into him when he had been on the way back with the shopping, groceries spilling onto the pavement, including Sherlock’s packet of disgusting Lapsang Souchong, only tea in the world that could taste like you forgot a burnt swamp corpse under your bed for a week -

“That - that was you,” John gasped, pointing at Moriarty (but mostly earned himself a bored and condescending look from the ferret and a slightly kinder version of it from the otter).

“But that of course changed after a little mishap,” Sherlock’s eyes roved briefly, pointedly over Moriarty’s body, “probably volatile components, so easily breathed in - unfortunate beginner’s mistake when you haven’t personally been dabbling in chemistry before,” Sherlock said, whiskers giving a smug little twitch. Moriarty gave a little hiss in response.

“So now it’s been you trying to turn yourself back,” Sherlock said, finally stopping just a foot from the ferret, “And I’m offering myself as the test subject.”

“Kcht?”

“What?”

“Rowr?” even the badger in the bin questioned.

“It’s either my death at your hands, or me only returning to my human form at your mercy,” Sherlock stated, before leaning in until he was within paw’s reach of Moriarty, his voice dropping even lower. “Tell me that isn’t tempting.”

There were, interestingly, quite similarly strangled noises from both the mouse and the ferret.

“Sherlock, what - no, don’t-!” John tried to call out, but he was helpless, his gun still out of his reach under the bench on the other side of the room. Getting there would take too long and Moriarty could have injected either of them -

“Let her go and I’m yours,” Sherlock said, and why did that man always have the weirdest tensions with his enemies, John wondered desperately, but then Moriarty had already dropped Molly (who squeaked and scrambled away) and instead grasped Sherlock by the scruff of his neck.

“Kch. Chh-chhkrrt,” Moriarty said, gazing down at Sherlock - the ferret was holding the young otter now in a grasp that looked like an animated Disney movie with cute talking animals had abruptly decided that its plot was written by Stephen King now, Sherlock bent uncomfortably backwards with Moriarty’s paw pulling him down by the fur of his neck, forced to bare his throat to the ferret above who was now sliding the tip of the syringe almost lovingly along his cheek.

“KchCh. Krkch?”

“Just a few, actually,” Sherlock drawled, somehow looking markedly relaxed in the face of a possibly deadly syringe. “Are you familiar with Plautus?”

“Prrchts?” the ferret asked, now looking just slightly taken aback.

“Roman Playwright. Not terribly interesting man, but relevant to my last case. Haven’t quite deleted everything to do with him yet. I do remember a quote.”

Sherlock. Only Sherlock would turn a situation like this into a lecture, John thought, but he didn’t say anything, carefully kept his eyes trained only on Sherlock, because he could see what he was planning. Fortunately, the bin-badger couldn’t.

The otter tilted his head back even further, now peering up at the ferret with what almost looked like amusement. “Have you ever heard the phrase ‘It’s a poor mouse that entrusts its life to only one hole’?”

Which was the exact point where Molly had managed to silently tip-toe her way towards Moriarty’s back and sank tiny, tiny sharp teeth deep into his tail.

Moriarty screamed and dropped the syringe.

Sherlock gave a sort of battle squeak and attacked.

“What.” John's mouth stood open as he watched, paralyzed, as the otter hurled himself at the ferret, the ferret gave a high-pitched, answering screech and then both animals turned into a sort of rolling ball of furry death on the lab bench.

The lab bench… the sink of which behind them had become an overflowing pool, the water thundering down from the broken pipe above long having exceeded the drainage capacity of the basin. Now water was flowing freely over the rim of the sink, flooding parts of the bench and gushing onto the floor of the lab. The two animals were now locked in upright biting combat, staggering toward and wrestling with each other on the rim of the sink, to Sherlock’s right the overflowing basin, to his left the water splashing into the deep.

“Sherlock!” John screamed, one hand outstretched while he was still pressing down the lid on the honeybadger-bin-situation with the other, but he could already see it was too late, he would be too late, as before his eyes the most brilliant mind and his nemesis criminal genius were engaged in battle, getting ever closer to the edge - and then they fell.

To be continued...

Chapter Text

“NO!” John howled as Sherlock went over the edge of the lab bench, his slender form flailing, trying to find purchase in the air where there was none, water from the broken Reichenbach-boiler system splashing all over the falling bodies in their descent as if it was a merciful curtain meant to obscure the horror.

John’s voice broke and Molly gave a squeaky scream as Sherlock and Moriarty hit the bottom of the waterfall. The impact was like a thunderclap in the laboratory, John’s mouth standing open, Molly’s tiny mouse-paw from her perch uselessly extended as if she could have stopped the fall even if she had been closer, but now there was nothing but silence and rushing water.

John’s knees threatened to give way at last, his muscles frozen in shock despite all his years on battlefields, his mind for a second unprepared as be beheld the unmoving body of his best friend on the floor, inquisitive eyes closed now, lying next to the just-as-still form of his archenemy who he hadn’t been able to defeat in life, but now...

Of course, it was then a bit anticlimactic (but technically very unsurprising) when the squabbling of the two temporarily-stunned mustelids started only a second afterwards again, both sausage-shaped geniuses still intent on tearing the fur off each other after their fall from roughly four feet up.

It was at this point that John (who in hindsight had no idea why on Earth an otter falling off a goddamn lab bench had had him actually worried this much - he needed to see his therapist on monday, stat) decided he'd had enough.

With a heave, he grabbed and lifted one of the rolling office containers from under the table next to him, placing it firmly on the lid of the trash can with the honey badger inside it. Then he strode over toward the budget version of Watership Down still playing out under the overflowing sink and grabbed Moriarty right around his skinny, furry neck.

“Right. Stop it, you two.”

“No! John, I almost had him-!” the otter protested from the floor, waving his paws up at John in indignation, also seemingly unaware of looking like a wet rat that had been through a blender, patches of fur either missing or plastered to his skin.

“What you almost had is probably rabies,” John shot back, glancing around as to where to put the evil whiskered mastermind-

“ChCHchCHcH-!” the ferret contributed.

“Well, well, no need to be a sore loser,” Sherlock commented haughtily to the animal writhing in John’s hand above him. The ferret stilled for a moment and looked at him, murderously (but then, that was how ferrets looked most of the time).

John frowned. “What did he say? I still don’t get why you can all understand each other, by the way. Or anything else about this, for that matter.”

“I wouldn't care to translate. It was a bit...derogatory to your lineage,” Sherlock commented, while John now also reached down and allowed Sherlock to climb up his sleeve to settle on his shoulders again.

“Derogatory to my- Sherlock, out of the five people in this room I am the only one who is even bipedal and he is insulting my-!” John began, staring disbelievingly at the ferret now rolling its eyes in his grasp, but Sherlock interrupted him.

“Doesn’t matter. What does matter is that he may have indeed managed to finish the antidote to our shared current condition,” Sherlock said, indicating the open metal suitcase and its vials and syringes on the table in the middle of the lab. “Put me down on that table, John, will you,” the otter continued as he scurried down John’s outstretched arm again and weaseled over to the suitcase. “And put him…” the otter waved a dismissive paw toward the ferret, “I don't know, under a vacuum bell, maybe. We don’t have much time.”

“Not much time for what?” John repeated, confusion mounting again after the immediate adrenaline was wearing off. “Until the lab inevitably floods?” he asked, stepping back from the ever-widening puddle on the floor.

“Until the authorities get here, all of this research is sealed away and testing and approving this possible antidote to my current condition for use on humans will take weeks or months,” Sherlock said, eyeing the syringes and other contents of the suitcase carefully. “I do not cherish fish for three meals a day and while Moriarty has almost certainly disabled most of Bart’s alarm systems, I doubt we have long until we are discovered. We need to turn Molly and me back before then.”

“Wait, what?” John, who had, after some consideration, placed Moriarty in an empty cage obviously meant for lab mice, then carefully picked up Molly from her hiding place behind a Bunsen burner, turning to carry the little mouse over to the table Sherlock was sitting on. As tiny mouse front paws were gripping onto his upright thumb for balance and safety, he halted. “Sherlock, that ‘antidote’ Moriarty has been testing so far killed all its subjects.”

“Yes. Though looking at his research, I have reason to believe that this time, he finally got the formula right.” There were more arrogant-sounding ferret noises from the cage, but Sherlock ignored them. “Inject me.”

“Sherlock,” John swallowed. “I’m not - you know I - I’d kill to save your life, but I cannot inject any human - or, usually human - any person with a potentially lethal drug,” John took a breath. “Even if it means you have to stay an otter for longer. I’m - I’m your friend, Sherlock, but I can’t do that.”

Sherlock looked at him for a moment, John aware of both of them probably calculating Sherlock’s chances of getting to the syringes to inject himself before John could stop him, but coming to the same conclusion.

“John.”

“Sherlock. No,” John said firmly, also lowering his hand to let Molly scamper off his hand onto the table with Sherlock. “This isn’t a debate. You could die,” he emphasized. “And I - I couldn’t live with that.”

The otter actually paused at this, giving John another long glance, even more opaque than when he had been human. Then he cleared his throat.

“Yes, well - have you actually looked at the formula of his serum yet?” Sherlock asked, whiskered expression drawn in a frown. “You’re my - you’re a doctor. You might be able to judge it as perfectly fine.”

“I have, and judging from my own vast medical expertise concerning metabolisms of people who have been turned into otters,” John paused, giving Sherlock a look -  the otter looked somewhat more hesitant now and neither of them quite commented on the slight correction in his previous sentence. John sighed. “Okay, no, I don’t think this serum would kill you. But I still won’t inject you with it before it hasn’t been researched more thoroughly,” he defended himself, raising a hand when Sherlock had already opened his mouth again. “You will just have to wait.”

“...John.”

“No.”

“John,” Sherlock said, and now it sounded like the otter was swallowing. “I might...not have that much time.”

John froze. “What.”

“When Moriarty was talking earlier, he implied that I needed the antidote soon, because the formula he laced my tea with might very well make the transformation permanent if not reversed within a certain time frame.”

“...literally none of this is how science works.”

“This is also what you said about me turning into an otter two days ago. John. I need that injection.”

“A certain - did he say how long?” John asked, gaze flickering over to the ferret in the glass cage, but Moriarty was watching the proceedings now with what appeared to be only mild interest.

“Well, he wasn’t exactly forthnuging with-” Sherlock broke off. And stared at John in alarm.

“Did you just-?” John could feel his mouth run dry.

“I…” Sherlock, for once, looked somewhat struggling to keep calm. “I donug.” He stopped himself again, then looked up at John, eyes wide. “John, help me.”

“Squeak?” Molly interjected, seemingly gesturing at John, trying to get his attention. “Squeak! Squeaksqueak-!”

“Molly, I donug - I don’t know how lonug you have, I nugnug - John, please!” Sherlock looked up at John. “Don’t let me lose my mind,” he whispered, grasping one of John’s sleeves with his paw.

“Sherlock, I-” John could feel his heartbeat ratcheting up worse than during his fight with Moriarty’s badger-for-hire, the sheer fear in Sherlock’s voice feeling like ice water in his chest. “What if I- what if this serum-?”

“Jonug - John,” Sherlock managed. “I nugneed you to nug this. I- nug. Nugnug,” he said, and then clasped his paws in front of his mouth. “Nug,” he rasped, sounding horrified.

“Squeak!” Molly also cried, waving her forelegs at John, obviously in distress, and John made a split-second decision.

“Alright. Fine. Come here,” he said, glad that his years of service as a combat medic at least meant that his hands weren’t shaking as he prepped a syringe from the suitcase, no matter how much his heart was racing. He shot a glance at Moriarty in the glass cage.

“If this doesn’t work, you’re next,” he snarled, to which the ferret returned an unimpressed stare (as most ferrets will). “This is like Doctor Dolittle if H.P. Lovecraft had written the thing,” he muttered then, turning back to Sherlock with the syringe in one steady hand, the other just slightly shaking as it came down on the otter’s back, stretching the skin on Sherlock’s flank. If this didn’t work...

“Nugnu-John,” the otter said, forcing the words out with visible effort looking up at him. “I-nug,” he grit his teeth, “- I trust you.”

“I know,” John said and pushed the needle inside.

The effect was almost immediate. On the table, the otter gasped, and then abruptly started expanding, new swathes of pale skin bursting forth as no new fur was growing to cover the lengthening limbs, neck or torso. The snout was receding, eyes enlarging, hair sprouting from the top of the head in recognizable dark curls, the entire transformation looking as mesmerizing and queasiness-inducing as Moriarty’s henchman’s had, only now it was slightly ameliorated by the fact that each body-part ended up looking right and familiar when it finished changing, until finally...

“Well,” Sherlock said in a hoarse voice that at last spoke English again, half-sitting, half-slumping on the lab table with his legs curled up sideways and keeping himself upright by leaning on his hands, head still hanging down and panting, but looking only slightly the worse for wear, “That...seems to have worked.”

Molly squeaked. It sounded actually remarkably like she had when human.

“Ah,” Sherlock blinked, then looked down at himself. “Well. Technically, that was to be expected. John, hand me one of those lab coats, will you.”

“I...have never seen a mouse have a nose bleed before,” John replied a bit non-sequitur, staring at the dazed little animal now fixated on his friend.

“Lab. Coat.”

“Right.”

xxx

“So, how much time do we have until we have to inject Molly?” John asked as Sherlock was buttoning one of the lab coats shut, eyes roving once more over the formula papers. “And is it already too late for Moriarty and his hench badger?”

“Ah. Well.” Sherlock briefly looked away, curiously now appearing slightly more awkward than when he had been completely starkers. “About that.”

John could feel himself halt in his movements a second time.

“...Sherlock. Did you-” he turned to the mouse, “Did he-?”

“Squeak,” Molly said, the mouse also giving Sherlock a very flat look, little front paws crossed. “Squeak squeak,” she pointed out to John, who thought he didn’t need a translator this time.

“Yeah, you tried to tell me. Sherlock! You lying-!”

“Look, if you hadn’t been worried this process could actually turn irreversible I might have had to wait for weeks for them to finish testing and I really didn’t want to be an otter anymore-!”

“Do you KNOW what you put me through!” John shouted. “What if I had killed-?!” He stopped himself. “You. When we get back I’ll put you back into that stupid bird cage, all six stupid feet of you, you-!”

“John,” Sherlock interrupted him, looking unfairly commanding even if dressed in nothing but a lab coat. “Before you injected me. I meant what I said.”

And that, sadly, was really very hard to truly stay mad at.

“I should have had you neutered.”

(Which of course didn’t mean John wasn’t going to try his hardest.)

xxx

“Okay, so, uhm. I think these are yours?” John said a few minutes later, looking away as he handed Molly (now also fully human again and currently clutching to her front the lab coat they had put her under before John had injected her), her clothes he had found in the lab next door.

“Th-thanks,” Molly replied in a shaky voice, shuffling behind the privacy of an opened cupboard door, while Sherlock (who had mostly just bothered with barely buttoning the lower half of his own coat shut and was now staring at Moriarty’s notes in fascination) was barely paying attention to any of this.

“Okay. Sherlock?” John asked, at least getting a (“Hmm?”) from his human-again flatmate in return.

“As soon as Molly has put her clothes back on we need to leave, because there is simply nothing of this night that we could explain to any court, ever,” John insisted, “But... what do we do about...them?” he asked, gesturing at a very resentful, bored-looking ferret in the mice tank and one (presumably) still ticked-off badger in the bin.

“Oh. Right,” Sherlock said, for the first time seemingly becoming aware of their opponents again. “Hmm. I say we leave Moran here for Mycroft or any other of his minions to handle, but…” he pursed his lips then stretched out his hand. “Phone.”

“Wha-?” John began, already passing the gadget over to Sherlock out of habit, the once-again-human detective letting his fingers fly over the screen with ironically inhuman speed. There was a dial-tone and he lifted it to his ear.

“Mrs Hudson? Yes, I know it's late, but...say, could we discuss this rule about pets at the flat again...?”

Fin