Summary: A case plunges Sherlock Holmes into the world of things that go bump in the night, things that John Watson is familiar with, things he does not want to encounter again.

A/N: This fic is the product of too much Supernatural, and wanting to throw Sherlock into a world with real monsters who go bump in the night. You don't need to know of Supernatural and Dresden Files to read, really. Have fun, I hope! :)

The sky had taken on a sombre greenish-grey tinge as rain fell on the city of London. Everything was simply wet and miserable, and so was John Watson; soaked through his shirts and jumper, despite his coat and one good umbrella.

Sherlock, on the other hand, was absolutely buzzing with excitement despite the dull morning, walking with a slight hurried spring to his step visible only to those who knew his habits.

It really couldn't have come at a better time, John mused. Sherlock had been ready to tear the flat apart using only dental floss and a belt buckle.

John gave a long-suffering sigh, and quietly whispered to Sherlock that it simply wasn't decent to appear absolutely ecstatic about a murder. Sherlock glanced at him despondently, like a scolded child, but partially reigned himself in. He straightened, and walked towards the crime scene with the sort of arrogant air he took with him everywhere.

Greg greeted them with a nod, telling Sherlock to "behave", and raised the crime scene tape. "It's the same MO, a knife wound to the heart, the victim's prints all over the handle of the blade." Greg sighed. "But it can't be a suicide, because the angle - "

"The point of entry and the strength of the stabbing does not correspond with self-inflicted wounds - I can see, Inspector." Sherlock interrupted, crouching beside the body. "It is very difficult to stab yourself through your own ribs."

Greg shook his head, obviously exasperated. "His name is Sean O'Malley, age twenty-four. He is, as you already know, the same man who robbed the bank at Battersea yesterday. And now he's dead."

"This is the fourth one, isn't it," John murmured, kneeling beside Sherlock.

The crimes were unique, and definitely down Sherlock's alley. The Yard hadn't called in Sherlock for the first murder, because it seemed to be an open and shut case of disagreement between two partners who couldn't quite decide how to split money after a robbery, despite the "partner's" insistence that he wasn't part of this score.

The second murder was a nineteen year old student who had robbed a bank at Canary Wharf. That time, Greg had spearheaded the investigation, and decided to call Sherlock after the forensic team had trampled in and out, giving Sherlock enough ammunition to berate the rest of the Yard's so-called incompetence.

The third death, which occurred a month later, wasn't discovered until two days had passed, after the rain had already flooded the scene and washed away most clues that might help.

This one, which occurred two weeks after the last murder, was untouched and had been left for Sherlock to do what he does best.

This victim lay on his back, eyes still open and staring at the ceiling. His chest was a mess of blood, the murder weapon - a knife with a swirling pattern in the handle - buried to the hilt in the chest. "Cause of death is a particularly messy stab wound that penetrated the ribcage and pierced the heart. We'll need more tests to determine how many hours it has been since he died." John said, reverence for the victim evident in his soft tone.

"And I am willing to bet that it would have been an hour after the robbery occurred. Again." Greg's hand found the bridge of his nose, and started massaging. "Sherlock, do you have anything- these are obviously not suicides, and I'm getting more and more pressure from above to find who's doing this."

Sherlock stood, hands casually behind his back as he gingerly peeled off his latex gloves, pulling them until they were inside out and handing them over to John. He told John to keep the gloves for analysis at St Bart's, and, with another sigh, John asked for a spare zip lock from the evidence team.

"I'll send a text." Sherlock said, still staring intensely at the body. He paced around the room, following unseen footsteps, crouching every now and again to inspect an infinitesimal speck with his magnifier. "This is magnificent."

"I'm sorry?" John spoke up from his position by the body. He was examining the long fingernails - there was some sort of residue underneath the nails.

"Magnificent. Serial killers are always very artistic." There was a look of subdued glee on Sherlock's face, the rest exploding behind his eyes. "Some leave the room clean, like a minimalist artwork, and it's up to you to find that black speck that would make everything tumble down."

"Did you find it, then, that black speck?"

Sherlock turned to look at Greg. "I assume you have seen the skin beneath the man's fingernails, from when he scratched his assailant in the face? Tell me the Yard isn't utterly hopeless, Inspector."

Greg rolled his eyes. "I don't need the obvious, Sherlock."

Sherlock's response was a split second patronizing smile. "The man's right shoulder has a large contusion from where the suspect has handled him, which I am sure you would find during the autopsy. According to what I can observe, however, your assailant is approximately 180 centimetres in height, around 70-point-5 kilograms - which is the same as your victim. But, obviously, he is significantly stronger than our victim, for the man handled the victim with relative ease."

Greg hissed through his teeth. "Are you telling me that this man's assailant is not the same suspect from the last attack? You said the last time that the woman was attacked by someone her own size, Sherlock! There is absolutely no connection except for the MO!"

"Could we be dealing with a cult or an organisation of sorts?" John asked. "Because that might be possible, couldn't it?"

"Brilliant hypothesis John, but no." Sherlock gestured to the man again. "The stabbing is precisely how it had been done with the last victim, and if we have different assailants for each victim, the M.O. would be slightly off." He smiled to himself. "No, this was done by only one person."

Greg blinked. "But if the weight and height differs - "

"And that's the puzzle, Lestrade, don't you see? That's what we must figure out!" Sherlock said, short of rubbing his hands together. "Contact me with any other developments. I need quiet. You know where to find me."

"You told Greg that you'll be at the flat." John said, leaning towards Sherlock across the lab table. The table was covered with a variety of brightly coloured chemicals and lab equipment, glass tubes snaking around cylinders and beakers. John gingerly moved his hands, making sure not to topple anything.

They never quite made it to the flat, as Sherlock told the cab to drive straight to St. Bart's. Molly had the lab ready, and greeted Sherlock with a shy hello. She politely told Sherlock to be quick his work and, if possible, clean up afterwards. Even though they had something of an arrangement with Sherlock, Molly's co-workers didn't appreciate half-finished experiments on pen ink splattered all over the lab tables, or particularly foul-smelling moulds left on petri dishes.

John didn't expect for Sherlock to go straight to the flat, of course, but he didn't expect that he himself would be stuck in St. Bart's either. Sherlock hadn't even given him anything to do. The man asked for John to stay, and that was it.

John glared at Sherlock disapprovingly. "Also, you stole some of the evidence, again, Sherlock - I felt those gloves, and there was something in them. You do know they actually need the evidence to properly convict whoever they'll catch, right, Sherlock? The investigation doesn't simply end after yousolve it."

Sherlock waved John away, focused on the slide he was examining. "I impliedI'd be at the flat. Lestrade won't need us until they're done with the autopsy, and Molly's clearly not finished with that. They have better equipment here at the lab. And of course I left some of the samples at the site, John, I didn't take everything." He frowned, and swapped the slide for another, and another, and another. "Interesting."

"Right." John stood up from where he was sitting. He didn't know what he was supposed to be doing there, anyway. He should do something more productive. "We're out of milk again, like we usually seem to be, so I'm going to buy groceries. Do you need anything, Sherlock?"

Sherlock didn't answer, and instead swapped slides again. John shook his head, and had actually grabbed his coat when Sherlock called for him.

John put it down. "What is it?"

"Look at this." Sherlock directed, gesturing at the slide. He moved aside, and John peeked into the microscope.

"A human skin sample. What about it?"

"Now this." He swapped the slides.

"What is it?"

"Human skin." Sherlock announced, and John looked at him in disbelief.

"No it isn't. This doesn't look human. More like scales, like reptile skin but- no, none that I've ever encountered. It's different; this couldn't be a sample from a human, Sherlock."

Sherlock pulled out the slide, and handed the sample over to John. "Look."

"This… this appears human." John borrowed Sherlock's magnifying glass, and examined the sample. "Or, at the very least…"

"Mammalian, namely humanoid, in origin, but the cells appear to have similar construction to reptilian skin cells, but not quite." Sherlock gestured to the slide again. "Which makes no sense. Must be some form of mutation."

He hopped down from the chair and went to the rack of test tubes that were on a rack to one side. Sherlock grabbed one of them, and gestured at the residue at the bottom. "I ran some chemical tests on it, and it is, assuredly, organic. It appears human, until you look at it under the microscope, not to mention the bizarre mucus underneath it. Dried out, but unusual to find under what appears to be a skin sample from someone's arm."

John didn't reply. He leaned back against one of the tables, and stared at the floor, appeared to be in deep thought. His hands flexed as they held the edge of the table, and John tapped a foot on the floor.

It couldn't be what he was thinking, but that was the only explanation. There was nothing else that could do this - it actually fit the crime, all of it. John pressed his lips together. It seemed like he had no choice but to tell Sherlock. This should be good.

"John?"

He passed a palm over his face, and looked up. "Sherlock, I don't think we should continue this investigation." He said, almost cautiously, watching for Sherlock's reaction.

Sherlock raised an eyebrow. "What? No. Why?"

"I just think that this one isn't for you."

Sherlock shifted towards John one of his calculating looks, watching him like he could see through every move he made. John stared back, crossing his arms. "Obviously, you know something. Something about this case disturbs you, or is it the perpetrator? Yes, it's the perpetrator. You know something about our killer that disturbs you, but you are not forthcoming with information, as you would usually be if you know something that may be of use regarding a certain crime. You would be eager to help. This is different then. But why? You're afraid of something. Real fear, terror even."

He gestured, punctuating his words with a wave of his hand. "You've been unconsciously clenching and unclenching your hand, attempting to quell tremors, since you've seen the skin sample that I've acquired from the crime scene, which was, by the way, found on the floor beside our victim. Even if the skin at first glance matches our victim, it obviously isn't our victim's. And that piece of information unnerves you further - "

John huffed, and straightened from his position. As fascinating as it was, John never did like it when Sherlock started ripping him apart with unwelcome deductions. "All right, Sherlock, all right, enough."

"What are you not telling, John?"

"You would not believe it if I told you - " He paused as Sherlock opened his mouth to protest, but John held up his hand. "- but I'll tell you anyway.

The doctor walked around the lab table and leaned forward, facing Sherlock, his face a bit obscured by the lab equipment. Sherlock grabbed a stool, and leaned forward, resting elbows on the table and folding his hands attentively in front of him.

John drew in a slow breath. "It isn't human or animal. Or plant."

"So what is it, John?"

John shook his head, anticipating the disbelief that Sherlock would show. "Other-worldly."

Sherlock didn't disappoint. He eyed John, brows wrinkled in scepticism. "Other-worldly?"

"Paranormal. Supernatural."

"Cryptozoology, parapsychology?" Sherlock half-smiled in amusement. "I didn't know you believed in such things, John, especially since you're a doctor, a supposedly scientific man."

"You agree though, Sherlock, that there are some things that science hasn't studied yet? Hasn't discovered?" said John, sounding tired. He'd had the same conversation with others before, and it always led to the same conclusion.

Sherlock nodded.

"This is one of those things. And due to how dangerous they are, science may never get the chance."

Sherlock merely raised his eyebrows in reply.

John could almost feel the scepticism and disapproval coming off Sherlock in waves with his stare, but he continued anyway.

"Fine, look. That creature, that thing, where that skin came from - it's not an animal, Sherlock, although you can contest that, but no, it's too sentient to be an animal - it's a shapeshifter."

"A shapeshifter."

"Yes."

The detective almost scoffed. "No such thing, John."

"Yes there are, Sherlock." John seemed to lean in a bit more, his eyes hardening as he tried to get Sherlock to just listen and believe. "They copy another person's form, and every time they change, they shed their skin, nails, teeth, hair. Like what you found, although this is the first time I've seen it under a microscope."

"John, I did not take you as a subscriber to thinking of fiction as reality." Sherlock said, batting John's argument aside. He sounded a bit bored, perhaps even disappointed, and he turned back to his slides.

John huffed. "Look, Sherlock…"

Sherlock turned to John, stopping the other man's next words with a harsh stare. "These sorts of things have no scientific basis, and so they cannot be taken into account. John, this is reality, this is not Ghostbusters."

Even if Sherlock's words sounded final, John was nothing if not stubborn. He was going to make Sherlock hear him, no matter how much the man swatted John's words away with his tone. "So how would you explain this, all of this?"

"I need more data."

John flexed his hand, refraining from throwing a hand up into the air in frustration. "You haveenough data. I am telling you the interpretation, Sherlock."

"No, I do not, John. If I am going to run with the current data I have, the only explanation so far is that we are looking at a cult of twins who kill each other after robbing establishments of choice." Sherlock's voice was cold, telling John it would be wise to stop his current line of inquiry.

Not that John would. He needed Sherlock to see, to know the truth.

"And the skin sample?"

"Irrelevant."

"Hang on - you just told me earlier that it's couldn't have been a cult because the stab wounds are precise and consistent, Sherlock, that there could only be oneperson."

Sherlock didn't answer, so John continued.

"You said once, Sherlock, quoting Spock (which, to this day, I'm still amazed that you've actually watched Star Trek)that when once you've eliminated the impossible, whatever remains, however improbable, must be the truth. And this is the truth, and I'm tellingyou."

Still no response from Sherlock. John wasn't even sure if his friend was listening anymore, but he continued anyway. Sherlock needed to hear it, even if he wasn't listening.

"Sherlock, I know you don't want to believe me but will you listen to me and trust me for just a minute? Just because you haven't seen or observed it with your own brilliant deductive skills doesn't mean it doesn't exist! I've seen things - seen them with my own eyes, right there, when I was in service."

John released a controlled breath of air, his arms tensing as he leaned against the table. He looked at the floor, closed his eyes, and remembered.

He had seen men's eyes grow black with a cackle, moving at inhuman speeds, gleefully tearing apart the enemy's army with their bare hands, ignoring any attacks brought upon their person. They only stopped when a black cloud billowed from their bodies, temporarily darkening his field of vision until it flew away.

He had watched a man who wasn't there go from bed to bed, taking the lives of John's patients with a touch on the heart, easing their suffering and helping them let go. It wasn't until he looked up who the man might be that John was able to make him rest.

Bleeding wounds on his arm faded as a man held his arm and took it upon himself, literally, each bone shattering before John's eyes as the man broke in front of him. And there was nothing John could do but watch, mesmerised, because the soldier's grip was too tight for him to move.

And those were just some of the things he'd seen. He wanted Sherlock to know, to understand, but he knew it was futile unless Sherlock had seen it himself.

If it hadn't happened to John himself, he wouldn't have believed, either.

"I've tried to explain it away, to rationalise it - but I know what I saw, Sherlock, I know what I saw. Everyone around me tried to explain away everything because they didn't know, didn't understand. It made them feel helpless, to face something like that, something out of their control, something they felt they could not touch. But they're wrong."

John remembered curling in his cot or sleeping bag at night, jumping at each shadow that approached. He didn't understand what was out there, and at first, he didn't want to. It was useless, he rationalized at first, to go against those sorts of beings, when they were so much strongerthan him.

He couldn't do anything, and it terrified the living crap out of him.

Until he realised that as a human, he had an advantage. He could think more creatively than creatures who had learned to rely on their extraordinary powers. He had books, the internet, knowledge at his fingertips - he could find out their weaknesses. He could use the arsenal at his fingertips, the guns and arms and bombs, and call on friends if needed. He could use his knowledge as a doctor, even - because supernatural being or not, one would have difficulty moving if your clavicle were dislocated or your carotid artery was spurting blood faster than you could create it.

He could defend himself by finding out what he needed to know.

"Acknowledging that they're real, that they're part of our reality - is the only way we can help ourselves, and that's the only way you can help these people, Sherlock, if you believed me. Right now, you've got a so-called solution that you like, and you're choosing to ignore anything that doesn't comply with it - these were your words, Sherlock. I'm telling you what is going on, you have to believe me."

Sherlock levelled a look at him, and there was a look of - was that pity? - in his eyes. "These are fairy tales, John. Mere fairy tales."

"I- You-" John sighed. There was no way he could convince Sherlock until the man had seen it with his own eyes. It meant that John was alone in preparing for the upcoming confrontation, and that was going to make it more complicated. He didn't know how Sherlock would react if faced with this revelation all of a sudden. All he hoped was that Sherlock would be willing to listen to his orders if needed. "Fine, Sherlock, alright. There are simply some things you have to see for yourself to believe, I get it, I understand. But still I hope to God you never meet one of them."

John grabbed his coat. "I need to do some research and get some supplies, prepare for this one. Text if you need me."

He had a job to do.

He had noticed when John left.

And Sherlock was disappointed.

He had long since heard of such arguments from different clients over the years, ranging from ghost hauntings to demonology. His clients, although usually with an actual case, were always wrong, and, quite possibly, a bit mad.

Of course, when he heard the same argument from someone he very well considered his onlyfriend, he was immediately concerned for John's mental wellbeing. Especially since he was so... insistent, upon these so-called facts that must not be facts in any way.

Whatever John had seen, if he did see something, must be entirely explainable, and certainly not by fiction.

But Sherlock couldn't believe he had judged thatincorrectly. He was sure John was sound of mind and body. He was also not a very convincing liar. So whatever this was, John believed it to be true, and Sherlock hadn't miscalculated, because John was, for the most part, absolutely fine.

As a scientist and a rational individual, Sherlock had to accept that science had neither solved, studied, nor seen everything, so it was possible that these things exist, of course.

Sherlock pressed his lips together and looked up to the ceiling. He packed his slides away in a slide folder Molly kept for him, and disposed of the rest of his little experiment.

As much as he wanted to believe John, he could not. There was no proof. John was right, he had to see it for himself, not that he probably would, because such things weren't real.

He didn't want to pity John, but he found that he pitied his friend. John obviously believed those things, and that only meant that John was fooled by something back then, and that meant that he'd lived with this belief for so long and wholeheartedly believedit. Sherlock was only glad that his friend wasn't one of those people who pointed towards the supernatural to explain everything, for that would be... difficult.

Sherlock turned off the light to the lab, and left.

One would think that after a run in with a serial-killing-cabbie, Sherlock would pay more attention to taxi drivers.

The cabbie swerved down an alley that he shouldn't have, parked, and flung open his door. Before Sherlock could do anything, the man reacted with almost near-lightning speed and yanked Sherlock out of the back seat. The man slammed him against the wall with force enough to daze him, white exploding behind his eyes. The man pressed his arm against Sherlock's throat, effectively pinning him.

Sherlock's gaze came into focus, and he was greeted with his own face, grinning at him with a macabre smile.

It was his face. Sherlock's face. It was like staring into a mirror, yet it wasn't, because this was real, definitelyreal, and Sherlock was sure that he wasn't given any sort of drug or poison at any point, unless it was in the cab, but he was confident he would have noticed any sort of poisoning - in any case, whatever this was, Sherlock couldn't deny what he was seeing right now.

But that wasn't important at the moment. Whatever was attacking him, it was trying to kill him. Especially now that it had pulled out a particularly long knife, similar to the murder weapons, down to the ornate pattern set in the hilt, aside from the length of the blade.

He'd just found his suspect. And, predictably, said suspect was trying to kill him.

There was no time to dwell on what his attacker looked like. Sherlock kneed him in the groin and wrestled himself away, careful of the knife his doppelganger had.

The man ran towards him again, raising the blade, hollering in Sherlock'svoice, which disconcerted Sherlock for a moment. He was almost too late in dodging the knife, and the blade grazed his arm. Incredibly sharp. It had cut cleanly through the layers of clothes. Sherlock moved to one side and took the man in a well-practiced judo throw, and slammed him onto the ground.

It was like the attacker wasn't hurt at all. The man swiped at him with the knife again, glee in his borrowed face. Sherlock jumped back just as the man stood up, almost lazily, and attacked again, brandishing the knife towards Sherlock's face. Sherlock ducked and turned, elbowing the man in the kidneys twice, and twisted to push the man forward.

The attacker recovered before falling over, grunting slightly at Sherlock's attack, and stood up, and came at Sherlock again. Sherlock whirled, batting away the attack, and slammed his hand into the man's throat, hard enough to choke a human. The attacker staggered back, and Sherlock used the opportunity to kick him in the stomach, hard enough to knock the man sprawling on the ground.

The man got up again, and went at Sherlock with another swipe of the knife. Sherlock dodged almost easily, blocking the knife with an arm, and followed up with a punch to the man's eye and another to his chest.

The man fell down, and stood back up.

Sherlock had figured that the man had enough stamina and strength to be sloppy. The attacker only needed to wait for Sherlock to get tired enough to make a mistake. Sherlock needed to find a way to incapacitate this one.

Anyone wouldn't be able to move properly if their patella was dislocated.

When the man came at him again, Sherlock was ready. With a slight turn, Sherlock crouched, away from the man, and gave him a direct blow to the knee. The attacker howled and staggered, but drew his knife out and caught Sherlock in the thigh, deep enough to make Sherlock fall back and limit his movement significantly.

The man, on the other hand, temporarily incapacitated, sat on the ground and tried to relocate his knee, and seemed to know what he was doing.

Sherlock knew he couldn't fight any longer, but tried to stand up anyway, leaning against the cab. He pushed himself up with a grunt, and backed away slowly. Maybe he'd be able to get to a street with more people.

The man had already re-set his knee, and even though obviously in pain, the attacker still stood up, albeit a bit unsteadily, and came at Sherlock with that knife again.

The unmistakable sounds of a gunshot rang out from somewhere behind the taxi, and Sherlock turned towards the sound. John stood in the mouth of the alley, gun steady in his hand. Sherlock glanced at the other man, who had fallen back and looked a bit dazed, a hole in his shoulder oozing blood. John walked towards the attacker and shot him in the leg. The attacker fell, and didn't make a move to get up, instead lying unmoving on the pavement.

"Sherlock?" John called, and Sherlock nodded to show that he was fine, despite the blood soaking his pant leg. He pulled his scarf off and applied pressure to the wound, wincing as the pain lanced up his body.

John gave him an answering nod, and walked to the other man again, kicking the knife away. He picked it up and handed it to Sherlock. "Get out of here." He said to the unmoving man. "Get out of here, and I won't hunt you. If I find you again, if you come back, I will killyou." John said. It wasn't a threat; he stated it as a fact.

The attacker growled in response, and grabbed John's leg. John shot it again in the arm, and dragged his leg away.

The man's arm scratched against the pavement, and Sherlock watched in astonishment as large chunks and sections of skin fell. Shed. Shed was a more apt description. John watched the attacker, staring at the skin, and then at the attacker's face, and looked back at Sherlock.

Sherlock closed his eyes. John was right.

Sherlock hadn't said anything on their way home, and John wasn't sure if that was normal. He hadn't seen Sherlock faced with something like thisbefore, and unlike the hound, this happened to be the real deal.

Even when John insisted on helping Sherlock with the wound, taking off his own jumper and pressing it atop the sodden scarf to help slow the already-sluggish bleeding further, Sherlock didn't protest. Not even a slight whimper, or the usual insistence that he was fine.

It was too quiet. John expected questions, he expected Sherlock to demand to know everything John did, to insist that what he saw wasn't real, to say something, anything.

God forbid that Sherlock was suffering through some form of psychological trauma. That would definitely be Not Good.

Sherlock remained silent as John stitched his thigh up, wincing just a bit when John applied the antiseptic and gave him a shot of local anaesthetic. He merely held out a hand when John gave him painkillers, and tossed them back without a word.

"Sherlock?" John tried, and Sherlock turned to look at him.

He wasn't sure what to ask next. 'Are you alright?' seemed inapt.

Sherlock simply gave him a slight nod, and told John that he was going to retire to his room. John frowned at him, but at the moment, there was nothing else John could do but to go to his room as well and try to sleep.

He couldn't.

Sleep didn't come easily, and when it touched the edges of his consciousness, nightmarish scenes played in his dreams. Seeing that shapeshifter brought back memories that he thought he was rid of, scenes of the war, of awar, just not the one he had volunteered to participate in. The one that he hadn't wanted to be a part of, but was anyway.

He had never hunted any of the supernatural, but it seemed that once you knew they existed, you would start finding them everywhere and you'd have no choice but to defend yourself and the people around you.

The first night that he arrived in London, he had to take care of a ghost haunting his sister's new flat, after it had killed about ten people who'd moved in and out of the place. That explained why it was so cheap.

The week after, a pair of hunters came by, almost accidentally, and had him patch up their wounds. They'd just dispatched a haunting down in Whitechapel, and incapacitated a werewolf a month ago somewhere in Edinburgh.

John had managed to get his hands on some charms and ways to put up a ward a few days after. He was careful, cautious, and when he moved to 221B, he didn't tell Sherlock, of course, but he warded the whole place. He stared at the etched symbols on his walls and his ceiling. Sherlock had asked about it once, but John had deflected his questions until the man left him alone.

John breathed. He was protected here. He was safe. Everything was going to be fine. But he still couldn't sleep.

He tossed and turned for a couple of hours, until he decided to sod it all and went downstairs to make some tea.

John was met with Sherlock curled on the sofa, reading a book. There were books everywhere, and his and Sherlock's laptops were on in front of the detective, who appeared to be very engrossed in his research.

"I thought you went to sleep." Sherlock said in greeting, not taking his eyes off what he was reading.

"Can't." John simply answered. "Tea?"

Sherlock gave him a nod. After a few minutes, John handed Sherlock a mug, and sat in his chair. "What are you doing?" asked John, even if knew.

"Research."

John couldn't stop the smile that started at the corner of his mouth. "On?"

Sherlock closed his book with a soft thump and looked up. "What do you think, John?"

John grinned. "All right, all right, no need to be like that, Sherlock."

They sat in comfortable silence. Sherlock flipped through his books, and occasionally looked at the monitors, swapping between laptops. John watched him, sipping from his mug. After a few minutes, Sherlock paused, and looked up at John.

Finally. John had been waiting. "You have questions."

Sherlock looked like he was holding back an eyeroll, but nodded instead.

John cocked his eyebrows in response.

"Why didn't you think that the Hound was some sort of supernatural being?"

John put away his mug, and leaned forward. "Well, for one, I'm not a lunatic, Sherlock." A smile twitched at the corner of Sherlock's mouth, and John smiled. "Two; there weren't any other reports of casualties in the area except for Henry's father. That's suspicious enough to say that it wasn't a werewolf or anything similar."

Sherlock made a slight humming sound in agreement. "How did you know where I was?"

"I followed you," said John. He knew that Sherlock wouldn't take any precautions against any attack, much less something supernatural, so he went back, just in time to see Sherlock board the cab with a cabbie that looked exactlylike him. He wasted no time calling another taxi to follow Sherlock to wherever the shapeshifter would take him. For a minute, he actually lost the cab he was following, and found Sherlock almost by chance in the alley. The grunts, groans and scuffles of two men that both sounded like his best friend had been the giveaway. He told Sherlock as much.

"Ah. Of course."

John half-hid a smile with his hand. "Yes, well, you needed to be protected from your own brand of stupidity and stubbornness, Sherlock."

"You have to admit it was pretty far-fetched John, if you do not believe in these sorts of things," Sherlock said off-handedly, reading off one of the laptops, his fingers dancing across the track pad.

John shook his head, smiling openly now. "In any case, Sherlock, I still foundyou."

"Yes, you did." Sherlock looked up. "Thank you."

John leaned back, satisfied. He peered at Sherlock from behind his mug. That wasn't the end of it, surely. "Is that it?"

"How do we confirm that it was, indeed, a shapeshifter?" Miracle of miracles, Sherlock was asking for his expertise. Not that he hadn't before - Sherlock always deferred to him when he needed a quick, trustworthy, medical examination of the bodies. But this was different - this was the supernatural. John raised an eyebrow at him. Sherlock almost rolled his eyes. "I am not an idiot, John. I can recognise if something is out of my depth, if I need help. Anyone who proclaims his intelligence but does otherwise is being pretentious."

John grinned widely and cocked his head. "Retina flare in the shop and bank cameras. I imagine that Lestrade's people would dismiss it as some sort of camera flare, reflected light. It's the best way to identify a shifter."

"Excellent." Sherlock seemed to have preferred to listen to John as the current expert rather than his thick books. "How do we incapacitate it?"

"We kill it. Him. Her. Silver through the heart. Bullets or knife, it doesn't matter." John had never been particularly comfortable with killing. Yes, he would do it if necessary, always, without fail. He would not lose sleep over killing someone who really did deserve it. But these creatures, no one even knew how their minds worked. Could they be reformed? Could they change? Do they deserve another chance?

There was a reason he didn't hunt. Everyone always thought it was as black and white as simply killing the offending creature. Ghosts, he had no problem with. They were mere shades of the person who was already gone. They needed to be put to rest. But those creatures? They were sentient. There were too many grey areas.

He preferred justice to retribution.

Sherlock broke through his thoughts with another question. "Where do we get them?"

"I know someone." John waved it away almost nonchalantly. He'd phone his source later.

He would have something ready for John. The man always did. He'd been the one who kept on telling John that he should go hunting. That John would be really good at it, with his accuracy, and his experience in the army. And John wasn't an idiot, which would help him even more than his target shooting.

John had refused, and merely collected enough things to help him protect himself and the people around him. It might be paranoid to line his room's window sill with salt, but it kept him safe. Not to mention all those wards. He had half a mind to change the door at 221B into iron, but that was probably overkill. Even if paranoia helped against monsters that want to eat your face, it might cripple you as well. Replacing the door with iron would keep the creatures out, but would trap you inside in case of a fire.

He glanced at Sherlock. John remembered the first time he was... exposed, if you will. The paranoia and the fear were crippling. It figured that Sherlock Holmes would take it all in stride, but still, with his reactions to the Hound, it wouldn't be remiss to simply ask.

"Sherlock, are you alright?"

Sherlock nodded, with a slightly raised eyebrow, as if he was wondering where the question came from.

John nodded back, but asked again, anyway. "Are you sure? If you want to talk about what you - "

"I'm perfectly fine, John." Sherlock said. He looked...energised, John supposed, would be an apt description. Determined. Almost manic, honestly, with his eyes shining and his lips trying not to quirk in a smile. "I'm handed a new worldto study."

Of course, curiosity. Scientific curiosity. Cures boredom, even Sherlock's. John gave him a look that wasn't quite a smile, but not neutral either. "Right. Well."

"John?"

"Hm?" John murmured. His eyes drooped. Tired. He might go back upstairs in a minute.

"I apologise. For not believing you."

That woke him up. It was like being soaked in a bucket of warm water, which wasn't altogether unpleasant. "I- It's fine, Sherlock, if it was me, I wouldn't have listened, either." John almost grinned. "It was a speech out of an urban fantasy novel."

Sherlock acknowledged him with a look that said a lot of things at once. "Will you tell me about the symbols in your room now? Did you ward it? We should do that to the flat." He said, gesturing at the walls around them.

John saved that tiny mental snapshot of Sherlock's face when John told him that the flat was already warded.

Their suspect had a pattern. After two-almost-consecutive robberies in a week, he took a month's break before the robbery. This meant that Sherlock and John had plenty of time to ascertain that it really was a shifter, and for John to tell Sherlock more stories about the supernatural.

He didn't have a lot, but John always had an affinity for stories and had heard more than enough about it to last a lifetime. Sherlock was insatiable. Their bookshelves were filled with new books on the occult, paranormal, preternatural, cryptozoology, parapsychology, along with all the crime books and miscellaneous things.

John taught Sherlock the basics of warding that he knew, and gave him a charm to prevent possession. Both men carried either salt or silver everywhere, or items of faith. They made sure to keep in touch wherever they heard something about the supernatural. The Homeless Network had more than enough information in that regard.

John had also made Sherlock promise that he would never take up hunting. Sherlock raised an eyebrow at this, and John merely shook his head no. "It's more dangerous and... addictive, than you realise. It's hard to turn back once you've started, and you, of all people, don't need more of that." Sherlock merely nodded and replied with an "of course, John," and that was the last said on the matter.

Greg finally brought around the set of security tapes for them to see, and Sherlock brought John's attention to the retina flares that flashes every time the suspect flashed across the scene. John indicated that he knew, and thus confirmed that it was, indeed, a shifter they were looking for.

John spread word among his contacts that he was looking for a shapeshifter. Sherlock spread word around that he was looking for someone whose retinas flare against any sort of camera, or a man who changes face.

They'd followed up more leads than was necessary. Most were either unrelated, passed on by lunatics, or were most definitely more thanshapeshifters. During those moments, John would urge Sherlock to run and leave. He wasn't about to face off against whatever those might be without being prepared. Let other hunters handle it. He'd call someone else in.

After a week or two, Sherlock had another case. It didn't involve anything supernatural, but it was bizarre nonetheless. John would never understand what would motivate a human being to be... inhuman, but he'd seen enough - too much, really, in his lifetime to know that humans can someone beat a demon at figuring out the best way to sin.

The shapeshifter case had been put aside for another day.

Somehow, everyone in Westminster had decided that today was bank day, and the queue was the longest John had ever seen it. He sighed. If this wasn't necessary, he wouldn't even be in the same vicinity of the bank. But John was depositing money as payment for the new supplies he'd received from his source. The man preferred bank deposits - never handled cash. John never questioned it.

John was actually a bit surprised that he was able to drag Sherlock along for him on this one. The man normally avoided errands such as this, spouting words like 'tedious', 'inane', or more often than not, 'boring'. Well, alright, maybe he lured the man with promises of introducing him to some of his sources, and to say that Sherlock had been intrigued would be an understatement.

When they arrived and John joined the queue, John couldn't shake off the feeling that something was wrong. His instincts were usually right, and he glanced around to see if there was anyone who'd potentially be a source of trouble. He told Sherlock that there might be trouble, mentioning their code word as he said some sort of nonsense to his flatmate. Sherlock had merely nodded, and glanced around as well, observing every movement, every person in the bank.

John eyed a man in the line, three people in front of him. Something kept on calling his attention to the man, and he wasn't exactly sure why yet. John glanced pointedly at Sherlock and directed the detective's gaze to the other man. He was almost frighteningly familiar, in a way similar to when one sees a ghost. John pressed his lips together, his hands twitching slightly. The alarms screaming in the back of his head intensified when the man drew apart his coat.

The man brandished a handgun in the air and started screaming for everyone to get down, levelling the gun at the manager's head.

"Press that silent alarm and I will shoot the bloody bank manager." He screamed, almost with a flourish.

John's eyes roamed around the bank, assessing the situation, watching the civilians first before levelling his stare at the gunman. He almost didn't notice that Sherlock's hand had clasped his arm tightly, and Sherlock had actually frozen as he stared at the gunman. John was going to ask him what was wrong, surely they'd faced enough gunmen, and this wasn't the first time they had been in a hostage situation - Sherlock usually bounced back quicker than this, but Sherlock merely nudged him in the direction of the gunman.

Bloody fucking -

The man was wearing John's face. John's face. With the ungodly sneer covering his expression, that definitely didn't belong on John's face, because John had never sneered like that in his entire life, nor had he ever been a huge fan of Glock pistols. He had also never considered robbing a bank, even when he hadn't eaten in three days because Harry was in that new private rehabilitation facility and he shouldered all the expenses-

Not-John's screaming brought John back to the bank. "Everyone to one side of the building. You!" He gestured to a man, making him stand up with a flick of his hand and his finger dancing over the trigger. He tossed a backpack to the man. "Help the teller fill that bag up with money. If I see either of you make an errant move to push that alarm - if I even see reliefin your face, I will shoot your kid."

John vaguely registered the gun swinging towards a child, who coiled further into his mother's arms in a foetal position. The mother turned, protecting her child from the man holding the weapon.

Another round of curses promptly somersaulted through his head. Not-John was threatening a child. A family.

Sherlock glanced at John, his eyes screaming in disbelief and fascination, seeing a shapeshifter at work in front of them, copying John's face and moving in not-John's movements. John ducked into his jacket when he heard whispers, something about a blog, and, dear lord, someone just spotted Sherlockand this was going to be a sodding mess...

Not-John seemed to be enjoying his damned time, one hand conducting an unseen orchestra. The gun in the other didn't waver. He was too steady, too good, and John couldn't see an opening. He needed an opening. Need to stop this before something went terribly, terribly wrong, even more wrong than a hostage situation and robbery in a bank. God forbid a murder.

Before John could even decide on another course of action, Sherlock stood up, drawing a pistol from his jacket. It took John several moments to recognise the gun for what it was, the one with silverbullets, the one that cost John quite a small fortune to acquire, way before he even met Sherlock. John was too busy staring at his best friend being the hero of the day.

Sherlock's 'sudden' appearance was enough to cause the shapeshifter a bit of a shock. The diversion was enough, and the shapeshifter lowered the gun just so, and John tackled the man with a move his rugby coach would've been proud of. The gun fell from the shifter's hand, and John couldn't have been happier that the drop safety was intact.

From the corner of his eye, he saw Sherlock stoop and pick the gun up, holstering it only god-knows-where because that bloody suit is far too tightto conceal anything, and John thought maybe it was why Sherlock wore that coat -

The shapeshifter clocked him one on the cheek. There was a slight sting, and John adjusted to compensate for his inevitable loss of balance. That one, he wasn't prepared for, his brain still trying to ignore that he was essentially fighting with someone who was him but not him. He firmly shook himself out of it, and let his limbs take over and stopped thinking.

His body adapted accordingly, and he turned that loss of balance into some version of a wrestler's throw, pulling his opponent's arm forward before it could even pull back fully from the punch he gave John. John handled him by the wrist, and pushed the man back down and falling unceremoniously on top of him.

His opponent groaned, but recovered just as quickly. He scooted out from underneath John, stood up, and was about to kick John in the kidneys but John rolled away. John stood and launched himself at his opponent again. He punched the man in the gut, followed with an uppercut to the chin that bruised John's knuckles, and used the heel of his other palm to hit the shifter's exposed throat.

His opponent grunted, taking it all in stride. He took John's arm and wrenched it back, forcefully enough that John was afraid it would dislocate his shoulder, knocking the wind out of John. The other person turned him around and hooked an arm around his throat, choking him. John jabbed his elbow into the stomach behind him twice, thrice, maybe five times until he let go.

John staggered away to breathe. The opponent lunged at him again.

He dropped like a stone before he even made contact with John. John glanced at Sherlock, who held the gun in his steady right hand, the other stuffed in his pocket. He jogged towards the shapeshifter and rolled him over, the shapeshifter coughing up blood that was just the wrong shade of red. Sherlock pointed the gun at the shifter's chest and fired.

The shapeshifter stopped moving. Sherlock aimed again, shooting him in the face.

John vaguely registered the slow cheers around them and the sirens he could hear in the distance. He was still staring at the dead Not-John in front of him, with Sherlock standing over the body.

John pulled the by now familiar, orange blanket off his shoulders. He exchanged glances with Sherlock, who looked very amused as he explained to Greg what happened. Greg looked like he was suffering from a headache already, even if it was just noon, and his eyebrows were scrunched together. John couldn't decide if Greg was in pain, thinking, or merely trying to shield his eyes from the glaring sun. Probably all of the above.

"And then you shot the suspect with his own gun, is that it?"

"Yes."

Greg raised an eyebrow. Sherlock rolled his eyes. Greg sighed. "Look, all right, we've all had a long morning. I'll just run by your flat later to get your statement - both of you." He glanced at John as well. "And it betterbe the complete story." He looked back at Sherlock. "Have you got anything more on the murders?"

John knew he was asking about the shapeshifter case, the one where the perpetrator was just killed with three silver bullets. Sherlock shrugged. "The killer seemed to have gone. I've nothing more on it. I was just a hostage in a bank robbery, Inspector."

It was evasive, and John and Sherlock knew that. It was almost the same line Sherlock fed Greg when they talked about the death of the serial killing cabbie.

Greg merely emitted another long-suffering sigh, and shook his head. "Later, Sherlock. I'll get your statements later." Greg left to talk to another victim, who was gesturing wildly at the bank as she told her story.

John turned to Sherlock, and pulled the shock blanket off the detective's shoulders too. They stood from their spots on the back of the ambulance, and began walking toward the edge of the perimeter to get a cab.

"So?"

Sherlock turned to John with seemingly-bored eyes, even though John could still see the last dregs of adrenaline seeping through in the way Sherlock kept moving his hands. "Hm?"

John looked at Sherlock. He wasn't sure if he should grin proudly and shout that whatever Sherlock did was fantastic, or wait patiently, hands clasped behind his back as Sherlock explained. "How did you figure out which one was me, and which one wasn't?"

"I used my phone."

John stopped, and blinked at him. "I'm sorry?"

Sherlock sighed, and glanced at John as if to tell him to keep up. "I used the camera on my phone and watched for retinal flares."

"Your phone." The hand in the pocket. Sherlock had a hand in his pocket. He must have slipped the phone back into his pocket.

"You didn't notice?" Sherlock half-turned to John, his eyes and his voice conveying surprise.

John sighed tolerably. "I was a bit preoccupied at the time."

Sherlock huffed tolerably, as well.

"Anyway...that was it? You merely used a camera to determine if it's me? You didn't find an errant spot on my shirt or - "

"Don't be ridiculous, John. Sometimes Occam's Razor is simply the best method to follow." Sherlock smiled a bit, as if he was enjoying a private joke. "I knew it was you from the quality of his clothes. Too new - but I could not observe properly until you both stopped struggling."

John smiled knowingly. "Right. Brilliant."

Sherlock turned with a dramatic sweep of his coat. "It pays to be thorough. I didn't want to shoot you, after all."

John gave a small wave to the constable manning the scene. The constable gave them a small salute. "Thank you." said John, almost wryly, and Sherlock smirked. Message received.

The shapeshifter was gone. Sherlock had destroyed the man's face, so that he didn't look like John in any way - or, at least, they'd have to run his prints and dental records first, and that would take some time.

All right, now John was a bit concerned. He didn't want the name John Watson emblazoned all over the Yard's files, that he was the perpetrator in a bank robbery. It would be conflicting to the fact that hewas also the one who stopped that robbery, as well.

John shook his head. That didn't matter as much. They'd take care of it later. Right now, the case was finished.

Sherlock realised, almost a day too late, that he needed help from very high places. He also realised that he'd rather jump from very high places than ask for help.

But he had no choice.

This left a very bad taste in his mouth, and he grabbed his phone and sent a text.

After ten minutes, his phone started ringing. Sherlock answered, and there was silence, like both speakers were simply challenging each other to speak first.

Sherlock thought that since he was the one who needed help, he should be reasonable. Maybe. "Mycroft." There was still no answer, and Sherlock didn't sigh. "I need a favour."

"Do you need help in cleaning up the mess it left, Sherlock?" The man on the other end sounded amused, and this irritated Sherlock to no end.

Sherlock knew that Mycroft knew what he was talking about, and who it was for. Mycroft knew. Some things didn't need asking. "Don't make me ask."

He could practically hear the smirk in Mycroft's voice. His brother was clearly enjoying this, and that made him all the more annoyed. "I'll make it all disappear."

The reply said more than it did. That was always how they talked as brothers. Hidden messages, secret clues, which only the two of them understood. He'd make everything disappear, that only meant he understood, which meant he was watching, which meant he knew and he didn't tell Sherlock.

The word familyslipped from Sherlock's thoughts like a disgusting swearword.

"You know," he said neutrally. He could almost see Mycroft nod from across London. It irked him that he didn't figure out that Mycroft, bloody Mycroft, would know about the existence of them, and he didn't say anything.

"We watch them, yes. Some slipped past before I could do anything about it."

Jokes about his brother's position weren't off limits. Jokes about his level of intellect weren't off limits, either. He'd always known his brother was smarter than him, not that he'd ever admit it. "I thought you were omniscient, Mycroft."

"Not omnipresent, no." He half-imagined Mycroft to roll his eyes. No, Mycroft had a smug look on his face, one that was only present if he agreed to something that Sherlock said as a joke, or when he was humouring Sherlock as he did even when they were kids, playing pirates with brollies.

"Why didn't you tell me?" It was less accusatory than Sherlock liked, and more than he felt. His brother always hid things from him. He expected it. Mycroft would say that it was for Sherlock's own good, like when he controlled and hid away most of the trust fund that Sherlock had, like when he flushed the cocaine down the toilet and carted Sherlock off towards the most miserable three months of his life backed up by promises of more cases from a well-meaning DI who had always kept tabs on him.

It genuinely surprised Sherlock when Mycroft was straightforward, this time. "It isn't something that I want you to get mixed up in."

"But-" He sounded like a petulant child. He didn't care.

Mycroft was stern. He hadn't heard his brother this stern in years. It made him feel like he was fifteen again. He hated it. "It's more dangerous than you think, Sherlock. Do not do more than what you have done now. I will not have you go hunting, not even to ease your boredom."

Sherlock was almost indignant, but he wasn't. He spoke slowly, truthfully, this time, and hoped that Mycroft could hear it in his voice. "I will not. They are not within my current realm of knowledge. I need more data, more information."

"If I give that to you, Sherlock, you will not use it to hunt." Less stern, but no less of a warning. There was an unspoken threat. Sherlock didn't want to know what Mycroft was going to take away this time, if he didn't heed his brother's 'advice'. Mycroft always knew what to take away, what would hurt.

"I would not. Hunting is not a puzzle; it's a war, and it's not mywar. But I wouldn't be remiss in giving away information to those who need it," he explained.

"I am not opening your eyes to something you're not ready for." His last warning. Mycroft always warned him in triplicate, as if telling him that he should be sure of what he was asking Mycroft, because Mycroft would give it to him, and he might not like it. Like that year he asked - no, demanded Mycroft to leave him alone. He didn't imagine that Mycroft would make him feellike he had been abandoned. It was painful to admit that he needed his brother more than he let on.

Those words made him indignant. Sherlock saw it with his own eyes. He was not an idiot, and Mycroft knew that those words would provoke Sherlock. Accusing Sherlock that he didn't know something he already did. It always made him say what was on his mind, exactly what was on his mind, without any semblance of filtering, to his brother. The words came out harsher than Sherlock meant. "I am a rational individual, brother. I saw it, felt it, heard it. I killed it. I was not drugged, nor were my senses lying. I believe what I saw. Keeping it from me will not help, especially since once you know about them, they will always turn up, according to someone I trust. I need to take precautions, know what I may be up against."

"I advise you to be careful, Sherlock. You're playing with hot water in a particularly fragile glass." Resignation that only Sherlock could hear and identify. Mycroft agreed, and Sherlock was pleased.

He meant what he said. "I will."

Beta'd by hopeinashes and shwatsonlocked. Thanks!