A/N: I will admit, I particularly like the idea that Sherlock is an asexual, in love with his work kind of man. But I do believe he's human, and taking care of human needs is just another way of maintaining his focus. I think he just happens to think taking care of it by using John is a better option than anything else. Plus slash is just fun.
Nothing alarmed and disturbed the detective's mind more than what he was experiencing then. Living with John he had borne witness to such moments before - passing by his room late at night, barging in to run an idea by him, stealing his bathroom when his own wasn't working to speculation - but never, never had he heard John utter his name.
The effect it had on him was… incomputable.
Sherlock stood flattened against the closet door, his breathing carefully managed. On the other side of the thin, cheap wood John was touching himself, hand wrapped firmly around a - Sherlock had to confess - impressive specimen of the male reproductive system, gaze focused on what the detective could only surmise was an imagined version of himself. John? Attracted to him? Pleasuring himself to the thought of him? He couldn't help but be curious as to what the good doctor was imagining that was working so well for his libido. He might have asked him - might have stepped into the room just then and savored the look of shock on John's face as he messed himself in front of him - his lips turned up slightly at the thought. But no… Sherlock had things to do, business to take care of.
He would have to deal with John and his fantasies later.
It wasn't long before John had finished and dozed off, and Sherlock breathed a silent sigh of relief. Creeping out of his hiding place, he picked his way across the minefield of John's personal belongings. He stumbled a little, knocking a pile of books by the bed onto the floor. Luckily for him, John was a heavy sleeper when his body was surging with testosterone. But Sherlock frowned. His balance was off, his movements awkward. What in the world - he looked down at his trousers, frown deepening as he spotted the large protrusion in the cloth. He reached in and tucked it up so it would snag underneath his belt instead of bobbing awkwardly. Well, no wonder he was feeling so cumbersome.
He left John's room, closing the door with a click. He hadn't been expecting that, not at all. It derailed him, and it took a few minutes he could have used for preparation to recenter his mind.
When he entered the living room, the young surgeon was perched on the arm of John's favorite chair, Sherlock's old skull in his hands.
"Did you like what you saw?" he asked, nodding at the still-obvious bulge in Sherlock's pants. Formal suit pants were terrible at hiding erections, but Sherlock so rarely needed them for that purpose.
"I believe we have more important things to discuss."
"On the contrary, Mr. Holmes," said Niles, stepping away from the chair and raising the skull to his face. "I believe your relationship with John is exactly the reason for our meeting here this evening."
Sherlock narrowed his eyes at the young man - he looked like a boy next to him, tall, yes, but young in the face, his face looking almost innocent but for his eyes. His suit was neatly pressed and expensive, his shoes meticulously shined. His hair - and that awful shade of green threw him off - was mussed in a purposeful kind of way, bangs in his face just enough to annoy the detective. He exuded confidence, standing perfectly still and calm as he watched Sherlock deduce him. He read like a teenager, like a child, and like a professional - a nicely-wrapped bundle of contradictions.
Niles cocked his head to one side, and Sherlock read excitement into his smile.
"Well? What do you think? John's said you can tell everything about a person with a glance like that. What are you reading about me, Mr. Holmes?"
Sherlock took a breath, sensitive nostrils picking out the smells of rubbing alcohol and hospital.
"You're a doctor - a surgeon to be exact, and a good one. The heavy emphasis you place on consonants tells me you spent a good amount of time in Germany - studying abroad, no doubt, which would explain along with my observations of you and your patients why St. Bart's lets you keep that ridiculous hair. You're excellently skilled and well-experienced, and your patients love you, which is a plus for any hospital looking to improve their PR. St. Bart's did once house me in their basement, after all, and I'm sure you've heard what the media said of that." Sherlock ignored the Cheshire-esque grin Niles' smile had grown into and moved on.
"Your shoes aren't scuffed at all - in fact, they look brand new, and as most men recovering from a move to a new flat wouldn't dare spend the extra cash on new shoes - or a new suit, for that matter, both custom-made - I would venture that you've either a larger sum of money than you let on or a benefactor, in either case the money is also going to the upkeep of another place of residence entirely, where the majority of the things you haven't yet moved into your room here are likely stashed. Being a successful surgeon might explain a thing or two, but you're young - too young to have amassed that much, and even a medical prodigy can't make millions in a just couple of years. Either it's an inheritance or something more criminal, my personal inclinations being towards the latter, though most would disagree."
The detective took a short breath, his eyebrows furrowing slightly when he saw Niles' eyes rake down his body. He might have been reading him, making his own deductions, but he doubted the look was purely for the purpose of gathering information.
"Well, quite right, for the most part," Niles interjected, puppeting his words with the skull. "Family home in East Finchley, all mine now - an inheritance of sorts, you could say. Parents are alive and well, of course, but working in America and far away. Don't suppose they're ever coming back at all, either. But none of that is important, and none really quite relevant to our current situation."
The young surgeon closed the distance between them, locking eyes with the detective. He licked his lips and Sherlock felt uncomfortable, though he wasn't about to move backwards and let Niles believe he was intimidated. Niles leaned in, tilting his head towards the side of Sherlock's face - too close for comfort. The smell of alcohol was stronger, but the heat that radiated from him, the sense of desire - no, of hunger was far more overwhelming. The boy's muscles were tensed, his body taut - Sherlock could tell from the clear outline of his jugular - like a predator crouched, waiting to pounce.
"Tell me why I killed those people," he whispered in his ear.
He pulled away and Sherlock met his eyes, saw the challenge in them, the razor-keen edge that looked so out of place on a face that looked as kind as Niles'. The detective stood perfectly still, holding the younger man's stare. He was dangerous, if only because nobody would ever guess he was. Sherlock needed him stopped - or, at the very least, Sherlock needed him out of Baker Street.
"Bonus points if you can tell me how," he added, stepping past the detective and to the front door. Sherlock could hear the quickly approaching sound of a siren, and as Niles stepped away from him he went to the window, peeking carefully out the curtain to see two police cars go screaming by, the men in the car parked across the street from the flat leaving their vehicle to approach the front door, chatting hurried sentences into their walkie talkies.
"Dear me, it looks like something's happened," said Niles. "Do excuse me, Mr. Holmes, I'll only be a moment."
Sherlock watched as he stepped outside the door into the stairwell, closing it most of the way behind him. He heard the loud footsteps of the officers coming up, pausing when the saw the green-haired young doctor at the landing.
"Shh, sorry officers, flat mate's asleep. Bit rattled, you know, by all this. What's going on?" The concern in his voice was admirably genuine - Sherlock couldn't help but be impressed on how completely Niles could switch demeanor. He almost sounded a little rattled himself, which was a nice touch.
"Apologies, sir, but they've found him. He did in one more and then did himself - he's gone. We're going to the scene now."
The detective would have been floored by the news if he hadn't expected some sort of difficulty. He had been hoping the police surveillance would last a little longer - it would have bought him more time, made matters a bit more difficult for Niles - but the boy was clever, and had more connections than Sherlock had immediately realized. He was curious, overwhelmingly so, as to how he had managed to make another man take the fall. The Yard wasn't particularly difficult to fool, but suicides were tricky, murder-suicides even more so.
"Ah… good, that's - " he heard Niles expel a huge sigh of relief. " - that's wonderful news, officer. Thank you. D'you think when the DI's all done over there, he could drop by? I know my flat mate's probably going to want to have a chat with him about this when he's up and about."
"We'll let him know. Do you two need anything else just now?"
"No, no officer, I believe we'll be fine now. Thank you again - and have a good night." The smile in his voice was audible. Sherlock could imagine the officers' faces melting into smiles as well - irresistibly, even. Niles seemed to have that effect on people.
"People skills," said the detective as Niles entered the room. "It's your perfect alibi. You know how to carry yourself, how to inflect your voice, how to hold your face - it makes you seem normal, makes you fit in. You know exactly what to say and how to say it. People can't help but feel right around you. No one would ever want to believe you're capable of doing ill, and so they never will."
"Oh, Mr. Holmes, you flatter me," he said, and Sherlock was sure he saw a blush across his cheeks.
"You aren't flattered - not really. You knew that, all of it - you're just very good at appearing to be what you want to be. That's why they don't struggle, isn't it? They come to you willingly. They probably even ask you to do it. Though it seems a bit cheap to go after the terminally ill. Did you he offer to take the rap for you? Whoever they're on their way to find?"
Niles chuckled, tongue poking into his cheek for a moment as he thought to himself.
"You know, I had been considering trying my luck with a perfectly healthy, if a bit emotionally devastated one. But I've changed my mind. I'm rather fond of him now - bit of a thing for military men, I suppose. And that limp is God-awfully cute. And no, that one didn't really have much of a choice in the matter."
Sherlock's mouth twitched. The idea of him going after John was beyond irritating - and if Sherlock had brought a gun it'd likely be pointed at the back of his head. Sherlock wasn't usually one for guns, but sometimes they were called for - especially in the case of meeting dangerous sociopaths who'd moved in with the only man in the world he thought of as worth a damn. He took a step towards Niles, glowering at him.
"You will not lay a finger on that man."
"Oh my, protective are we? No - weren't you listening? I'm not going to hurt him, unless he asks for it… which he just might. It's those broken types, you know… such masochists."
Sherlock's eyes narrowed. He'd heard whispers of the young surgeon's sexual deviances, but they were only whispers, and he'd never laid his hands on anything concrete. Masochist. The word sent his mind running back to the Woman's riding crop and how intriguingly original the situation had felt, how it would, he imagined, feel for someone like John. Niles Cohen was a presumptuous young man, arrogant in a sneaky and underlying sort of way. It bothered Sherlock, not because the arrogance was unfounded, but because he had an inkling he was right.
"And what exactly makes you believe he's going to ask for it?"
Sherlock didn't enjoy the malevolence, the understanding in the surgeon's smile.
"I don't believe, I know… because you aren't going to tell him you're alive, are you, Mr. Holmes?"