Warning: Adult scenes in this chapter, please be cautious. Very graphic boy on boy sex. If you're going to be at all offended, I'd recommend you stop reading - there's going to be quite a bit of it from here on out.

A/N: Yes, I do take my time getting to the fun things, don't I? So sorry.

It was dark out when John finally returned home. To his credit, he had been working hard - asking questions, searching places, scouring the morgue at St. Bart's - and Molly, incidentally, who seemed determined to convince John she had something better to do - for clues. Sherlock might have been proud at how painstakingly observant he was being - except that John found nothing and no one that was helpful. He was frustrated as he climbed the stairs to the living room, lingering thoughts of Sherlock still weighing on his mind and his nethers.

"Niles, I might need your assistance with - " The doctor stopped mid-sentence, floored by the sight of the brunette sitting perched on the arm of his favorite chair, toying with what looked like a saber. The tall man's hair was wet, the moisture making its tips turn up, giving it the impression of slight curls. His chest was pale and bare, rivulets of shower water running down it, a towel draped about his shoulders - lean, muscled shoulders, and well-toned arms. Grey-blue eyes turned up to meet the doctor, sparkling with something fiercer than John had ever seen in them before, even if his expression played at innocence.

"Good evening, John. Been productive?" he asked.

"Your hair - " John began. The younger man stood, pulling the towel from his shoulders and approaching John. His smile was disarming, a level, subtle upturn of the corners of his mouth. A Sherlock-esque smile. John felt a tightening in his trousers.

"What do you think? The surgery asked me to try a natural color, and the blonde just wouldn't cover the green, so… here I am."

"I - " John swallowed. He was supposed to be taking the lead, wasn't he? What had happened to all of his confidence and determination? He cleared his throat, his hands clenching at his sides. "Good. It's good, yeah."

Niles' face broke into a sweet smile.

"Oh, I'm glad. It's a bit of a mess when it's drying like this, gets all curled up everywhere. But you were saying something - what was it you needed help with?"

John licked his lips, blinked his eyes, steadied his gaze on the man in front of him.

"Sherlock," he said definitively. It was all he could muster. Niles could smell the alcohol on him, he was sure.

"You want… me to help you find him?"

"No," John interrupted, then cursed and shook his head. "Well, yes, but - no. Right now - no." His eyes moved from Niles' and he let the gaze wander over his bare chest, down to his trousers and back. The realization came to the young surgeon's face and his eyes widened, the fire in them blazing.

"You want… to pretend," he said, and John hadn't realized his voice could get so low. It was wrong, of course - the tone, the cheekbones, the tilt of his eyes - but John could ignore those for one night.

"Yes," he breathed. "I do."

John had opted against the bedroom. Impatience and a modicum of respect for Sherlock's things kept him in the living room, where he had stripped off his jacket and his jumper. It was awkward and hasty at first, clothes shed and tossed to the floor, hands groping, but John called the memory of the detective up to his mind, remembered his voice, his face, the slope of his body underneath his dressing gown - and he was soon over the awkwardness. He had never been with a man before, but he was going to be with the detective tonight - his detective, and it was going to be alright.

Niles had removed his shirt, deft surgeon's fingers making quick work of those buttons and the fastening of his jeans, which John kicked off quickly. He reached for Niles' pants - dark blue pajama bottoms, silk - but the lithe body twisted away from him, grabbing the doctor by the waist and dropping him onto the couch. He pulled off his boxers and John gasped as the cool air hit his exposed member. He was hard already, stiff from long nights of frustration and days of thinking of the detective, his cock pressing firmly against the slender brunette's lips and gaining quick entrance. John felt a tongue, warm and slick, swirling around the tip of him, around the crown, over the shaft as the younger man slid up and down on the doctor, fitting most of his length in his mouth and partially down his throat.

"You've - you've been wanting this for a while," murmured John, his hands tangling in the soft dark hair, urging him forward. His hips canted into that mouth, his eyes half-closed from the pleasure. Niles was good, practiced - he'd done this before.

"Brilliant deduction," hummed the brunette, and John quivered at the phrase. He swallowed John up again, making the doctor arch and moan, the name escaping his lips and setting his body on fire.

"Sherlock…"

Urged on by the utterance Niles swept his fingers up his thighs, fingers massaging, one hand dipping down to cup and massage the sack dangling beneath the doctor's cock, then probe beyond, massaging the firm muscle of the perineum, pressing inquisitively against the puckered entrance to John's ass. The doctor's breath hitched and bucked up into the other man's mouth, leaking clear fluids all over his tongue.

"Yes, Sherlock, please - "

"Shh…" John found his lips captured by the brunette's, tasting his own bitterness behind them as his tongue probed his mouth. "From the potency and the amount, John, I'd say you've wanted this for quite some time, too…"

He loved the way he was picking him apart. He was different, so very different from the Niles John had been living with for the past month, so much like the detective: he was sharp, cold, methodical - which is what John wanted. But there was something else, something in the way he responded to John's noises, taking in his reactions, his eyes both hungry and analytical. There was something feral hidden in the coldness of them, and it made John feel more vulnerable, almost, than he was comfortable feeling. John let out a groan and Niles' finger gained entrance, began sliding in and out of him, making him shiver.

"God, I want - " he found his lips caught again, the voice speaking against them low and domineering.

"Quiet. I know exactly what you want."

The finger withdrew, was replaced by two. He was stretching him gently, the younger man's other hand and the - God, wonderfully hot - mouth helping him relax into the sensation. A few more minutes and the doctor was pleading again, a soft whine tugging out of his throat when Niles withdrew entirely.

"Come now, John, what do you deduce would happen if I just went in? Surely a medical man would understand the ramifications…"

The condescension in his voice was spot-on, and far too sexy.

Dark hair bounced as he removed his pants, applying a healthy amount of lube to both his cock and John's entrance. The heat from the gel made John squirm, the absence of pressure inside him leaving him wanting. And then, all at once, the younger man was pressing against him, making him stretch, fairly sizable and slender and smooth. John let out a cry as he slid into him, his legs wrapping around the slender man's waist and his hands bracing himself back against the couch.

"God, Sherlock!"

"How wonderfully tight you are, John…" he growled into his ear, pulling out and thrusting in slowly, again, and again, waiting to feel John's body melt into pleasure before picking up speed. John looked up once, caught the stare of the lustful grey-blue eyes and threw his head back in a wild moan as Niles' cock hit that spot for him.

"Sher-Sherlock!"

"Yes, John… that's it… say my name." It was a command, hissed against his cheek. John immediately obliged, the sound of the detective's name on his own lips making him tighten around the cock inside him, pulling a gasp from the other man.

"Sherlock - Sherlock!" Their rhythm was enveloping him, John losing himself to the pounding, the possessive grip the brunette had on his thighs. This was his detective, claiming him as his own, and John was loving every bit of it - and he wasn't going to last very long. He could feel himself sucking up tight, his shaft hardening in preparation -

John exploded all over his chest, sticky white fluids making trails up from his belly button. John barely registered when he pulled out, though the pressure of a towel and the sight of the young man hunched between his legs was a bit perplexing, even given the past few minutes they'd just shared.

"Oy, what're you…"

"Cleaning. Can't leave messes like this for Mrs. Hudson, can we?"

"And you…?"

Niles chuckled and shook his head.

"It's alright. It was your first time like that, wasn't it? I'm not going to go at you for as long as it'll take me. Easing people into this sort of thing is the best way to go, you know."

John laughed thickly. All of a sudden it was Niles again - considerate, compassionate, and sweet. He'd lent himself all too well to the dominance of the scene, and John couldn't help but wonder at how the kindly doctor he was used to dealing with could turn so quickly into someone else. He was also implying a repeat experience, which John wasn't so sure he was ready for. On the other hand, John wasn't so sure he wasn't going to want it again, either.

"Listen," John began uncertainly. "That - "

"Never happened, John." He flashed him half a smile before standing, the towel balled up in his hands.

"No, that's not what I was going to say. How - why did you do that?"

Niles stood from his position between John's legs, a queer smile on his face as he regarded the other doctor.

"It was sentiment, John."

"What?"

He grinned at the floor and shrugged, and John was sure he saw him blushing. He turned and started towards his room, tossing the sentence over his shoulder.

"When you asked me in the cab coming home from St. Bart's if I was being professional or sentimental… it was sentimental."