John was nothing if not practical. Some people would even say 'frugal.' He had come home from his half-day at the practice thirty minutes ago to find that his flatmate had turned the heating up very high, and then opened all the windows wide to regulate the temperature. The result was a dizzying, sickly heat interspersed with freezing, lip-numbing January gusts, and a suspiciously absentee detective.

Promptly, and with only the minimum required amount of quiet grumbling, John turned down the heat, closed the windows, and settled himself in his armchair. He was armed with a cup of tea in his extra-big mug, a knitted blanket from Mrs. Hudson around his shoulders, and his new letter-writing set, which he intended to make use of (if he could remember how to write a letter, that is).

The set had been given to him by Sherlock some weeks ago. He had wondered incessantly about where it had been bought from, until Sherlock told him glibly that he had lifted it from a client's drawing room. ("You know, that one whose face looked like that Dali painting where everything's melting.")

John had suitably reprimanded him, but softened when Sherlock insisted that he thought John would appreciate it more than Dali-face. John had reprimanded him again.

He couldn't hold the grudge very long though, because it was Sherlock, and for the man to even think of him briefly – if only to steal in his name – it was surprisingly thoughtful.

He took another lingering sip from his gigantic mug and set it aside, bringing his attention back to the little set nestled on his lap. The notepad seemed to be the main feature, the paper made to look like old parchment, with matching envelopes and a gold pen. It was all quite posh, for his standards, and the pen alone looked like it could have funded their fridge for a good week.

He set the envelopes next to his mug and twisted the lid of the pen, cocking his head as he tried to remember how he'd been taught to write a 'proper' letter. His address was supposed to be in it somewhere, right? To the left? No, that didn't seem right. To the right, then? It must be. And was he supposed to double or singularly space his sentences? John found himself frowning at the paper before the real question of who am I writing this to? stood prominent in his thoughts. That was a very good bloody question. He let out a heavy rush of breath before the notepad joined the envelopes to the side and his mug was once again resting firmly in his grip.

He had stayed friends with Clara after her divorce from his sister, and despite Sherlock's early innuendos, he had never been attracted to her. Now that she was living in Scotland with her new partner, it might be an idea to send her something a bit more thoughtful than an occasional text. He wasn't sure who else he knew to write to who wouldn't mock him for his quaint communication - but then again, people seemed to scoff at his technological acumen too. He couldn't win.

He would have to google it later. He could ask his flatmate, who would either be completely oblivious to the notion of writing letters, or be insufferably, public-school perfect at it. Sherlock wouldn't mock him, but John really hated being reminded of the things that separated him and Sherlock. In many ways they were identical, but in others, the gulf between them was vast.

He could almost see Sherlock's face now. The slight shift of his head, the way those eyes would look at him as if he were picking out the individual thoughts floating around his brain. He would want to know why John was writing a letter, either that or he would just ignore him completely. Always one extreme to the other with that man.

It only made the gulf seem wider. Sometimes he really had to question his own sanity when it came to Sherlock Holmes. He was the embodiment of the bizarre, with ultimate knowledge of one thing, and absolutely squat in others. He was a genius, but that intelligence was completely selective.

Just as John took another sip of his tea, he found himself shaking his head. Of course his thoughts would wander to his flatmate. If it wasn't for a letter, it would be for an action, or a reaction, or an insult. Any train of thought would end up backlogging all the way to the detective and John would be left continuously questioning himself and the reasons he was still sat in 221B.

His eyes flickered back to the notepad and he sighed, deciding that Clara would have to be his first option, because she was the only option he could think of right now.

The voice in his head that chastised him for being indecisive even with only one option before him, had, at some point, become Sherlock's. His flatmate had told him once that his own equivalent was Mycroft's sarcastic monologue that echoed in his Mind Palace through a separate sound system, with hidden loudspeakers, that he hadn't figured out how to disable yet.

He found himself smirking at that, because Mycroft's mere existence irked his friend, never mind always having that nasally drawl pounding through the halls without any hope of escape. He liked to think that he could understand the foundations for Sherlock's Mind Palace by now. Or he'd at least figured out a rough draft of what it could be.

John always imagined it would be a grand, sweeping palace, with rooms and doors and corridors draped in the finest silks. The most useful information would be stored in the biggest, most dramatic rooms, while the 'useless' information (like the name of the Prime Minister) would be shoved in a cupboard to the back. Either that, or it was something far more complicated that John probably wouldn't understand. He wouldn't ask, either, because it seemed the detective liked nothing more than comparing his own vast intellect to the apparent lack thereof where John was concerned.

He was just drifting out of his reverie, brought to alertness by the abrupt appearance of fat white snowflakes outside their grubby window (the size of the fingerprints on it suggested a certain detective's prior presence. Damn it Sherlock).

Feeling oddly content and languid, he was about to have another stab at letter-writing, when the peculiar and slightly-annoying rhythmic noise that had been going on for a few minutes, stopped. Only in its absence did he ponder whether there was some building work going on somewhere, but it sounded more...domestic than that. It began again, and he finally paid it his full attention.

The sound was low, could have been a humming if not for the slight hitch here and there. He moved himself forward, frowning as he focused. He realised all too quickly that the sound, now spiking in pitch, was being made by a human. Since there shouldn't have been anyone inside the flat besides the two people who paid the rent, John had to conclude it was Sherlock. Which only made his frown deepen. He was about to call out when something in the sound seemed to shift, and it started again. Louder, this time.

When he recognised, or thought he recognised, something...carnal? in the faint , rumbly noise, he felt a little sheepish that the first thing he assumed that was it couldn't be Sherlock after all.

Why shouldn't it be Sherlock? He was a grown man, why shouldn't he be...doing stuff like that in his own room? His curiosity was justifiably stronger than his shame at listening more intently. Anyway, he told himself, it could still be some burglar, who broke in during the morning to...have sex in Sherlock's bed?

Idiot.

Well, whoever it was, he decided, it certainly sounded... animate. John ran his tongue over the back of his teeth as the sound spiked again, this time it was definitely a moan. Oh, Christ, he thought as his senses heightened from the focus. Someone, who was still questionably a burglar, was definitely doing something quite, uh, intimate in the far side of the flat. Something that he probably shouldn't have been listening to.

There was a gasp before it mingled into another twisting moan, and John had to run his hand over his mouth. It would have been ridiculously immature of him to deny that it was Sherlock, now, even though those sounds and that man still didn't quite mesh in his mind.

God, who did he have in there? He strained his ears, and soon gave in, with hardly any shame, and went into the kitchen with his mug. If anyone happened to vacate (naked?) from the room, he could pretend he had just got in, was about to make tea, and was deeply affronted by this kind of smut, thankyou.

"Ugh...yes," came the deep, croaky plea from beyond the suddenly paper-thin door, or so it seemed. That was definitely Sherlock. Who else was in there? What were they doing to him? They were being very quiet...maybe their mouth was full.

Christ.

John hovered by the kitchen wall, the one that separated the two rooms, and found himself edging closer. He held the mug in his hand, in case said persons did decide to grab a glass of water before they continued their raunchy—

"Oh, oh, there."

John felt his mouth go dry, because the voice that belonged to Sherlock (really? Shit) was so breathy and wanton that it didn't fit any kind of image he had of the man. There were three quick gasps and a long exhale. He was one step away to having his ear to the wall, straining to hear the second party. They must have been doing something right, because Sherlock seemed as though he couldn't grab at any kind of rational thought. Christ, they must have been talented to have Sherlock Holmes speechless.

He couldn't deny that the two main conflicting thoughts in his head were juvenile, but really quite reasonable. Firstly - how come he never got fantastic midday blowjobs?

Because you don't have those cheekbones, he unhelpfully reminded himself.

Secondly...how could this be the first time he had known Sherlock to do anything even remotely sexual, in all this time? And who was it? Had he...hired someone?

Oh God, that would make so much sense, added his strangely-breathy inner voice. Sherlock wouldn't bed just anyone. They would have to equal him on some levels, if not on appearance then intellect or at least skill.

"Yes!"

John blinked and turned to stare at the wall, as if he could figure out this mysterious person. They must have had some true talent.

Where had he found someone like that? Would he tell me? Would I even ask?

If those moans were anything to go by, then yes, he probably would. Oh…but what if it was a man?

He nearly jumped out of his skin when Sherlock, so loudly that he might as well have been yelling in John's ear, howled. The sound was impressively extravagant, but it was raw, and genuine. John didn't think he had heard a sound of such honest pleasure from anyone, ever.

If John was feeling ashamed at listening, then Sherlock certainly wasn't doing anything to prevent that. Not that the man actually knew he was here. Did he?

The moaning no longer had the breathy edge to it, because something must have gone up a dial and now the man was groaning. Loud enough that John would have heard it from the living room. He blinked. Jesus, what was happening in there? He must have been having something amazing done to him to pull forth such desperate sounds.

His own burgeoning erection was almost an afterthought, a numb sort of thrill he was obtaining vicariously, from his flatmate's obvious ecstasy.

He was intrigued, almost concerned, when there was a wheezy silence. Thirty seconds passed, and the strangled groans started up again, with a sharp, hissed laugh, as though Sherlock couldn't believe what was happening to him.

John certainly couldn't. If he had been having as good a time as Sherlock clearly was, he would absolutely not be able to hold still for a bit of orgasm delay.

He was near enough pressed against the wall at this point, a small burn running a trail from neck to ears, because Sherlock had started up again with fervour.

He couldn't help but imagine what was happening, especially as there was now a small creak edging in to the moans. Something was moving the bed. John bit the inside of his cheek as an image flashed up behind his eyes, of Sherlock with some faceless stranger and the variety of positions that could make a bed move like that. The flush on his cheeks intensified, because now he felt like a creeper. One thing to listen, another to imagine. There was a strangled groan and John felt his own breath come out in a rush. Christ.

If Sherlock's partner was being unusually quiet (in John's mind they had a mouthful of consulting cock), the man himself was holding nothing back. He must have been close to his peak, because the decibels of his voice were rising as drastically as the pitch, till the snarled, choked yells were at the limit that his flatmate's deep voice could probably reach. John's ears were beginning to ring with the sheer volume. Good job I closed the windows.

He couldn't pick out anything over than guttural cries any more, and John had to take a moment to adjust himself. He never imagined Sherlock would be so... vocal. Well, he never imagined Sherlock would be into sex in any way, if he was honest. Not that he imagined Sherlock and sex together, anyway.

"Yes, yes, oh fuck!"

John felt his body go rigid as the curse came out just as swiftly as the other pleasured cries. Hearing Sherlock swear, in that strained, deep voice, was bizarre and unreal and Jesus, he was hard.

Complete words were clearly getting to be too much of a strain on the detective now. John was rapt.

"Y-Ye...Yes! Uh...oh...F...Fu...!"

Jesus Christ, shit, the man was going to have a fucking orgasm. The simplest and purest of pleasures had been transformed by the factor of Sherlock into something rare and astonishing.

John felt like he was on the tip of his toes as he strained to listen, even though the man's cries were loud enough to fill the whole damned flat. Was Sherlock squirming? Did he push his long, lithe fingers into the mysterious person's hair?

The doctor ran his tongue over his lower lip, barely registering that his own breathing had started up an uneasy rhythm. He didn't have the chance to reflect on much, because Sherlock let out a howl which would have been heard downstairs, even through the doors.

"Shit," he muttered to himself, completely gobsmacked by the sheer ecstasy in the detective's cries.

God, if Mrs. Hudson was here, he'd be in for it later. It would be adding insult to injury that, contrary to her beliefs, he was not the one delivering the mind-blowing pleasure.

How often did he do this, anyway? Every time John was out? Once a week? If he was purposely keeping it from John, maybe he was aware of his own...expansive responses during sex.

There was a breathless, tension-soaked pause behind the door, then one final, hoarse scream that was the moneymaker. Uncontrolled thumps of mattress, pained growls, grunts, and sobs of exhaustion and disbelief.

John marvelled at the power of that climax, and his cock reminded him that it would really, really like some attention soon.

He could still hear Sherlock gasping for air as he pressed his palm against his trousers, hissing at the contact. Shit, the man had a voice made for porn.

How had he not heard that before, though? He didn't think Sherlock was into sex or anything surrounding it, but the rustling of sheets told him otherwise.

…Were they kissing? Would Sherlock return the favour?

Why did the thought of someone else's voice suddenly make his spine snap taut?

John swallowed thickly, forcing himself to step away from the wall. He needed a shower, where the spray would actually mask his voice rather than have it vibrating against the walls and wailed into the street below.

He was mildly surprised when he heard (admittedly staggered, heavy) footsteps, a few cracks and pops of over-worked joints, a massive, satisfied sigh, and the door to the bathroom open and close. Sherlock distantly turned on the shower.

So much for that idea, then, he thought. Still...bit rude of him to just...leave them in bed. He didn't even say anything to them.

John stood still, even though he knew Sherlock wouldn't hear him. He was still listening for another rustle of sheets, a huff, or a groan. It was entirely possible that Sherlock had sated his partner beforehand and they were just lying there. Probably naked. John swallowed again, deciding that his curiosity was piqued enough for him to actually go and find out, and that it would be better to definitely not do that.

Even with Sherlock under the spray of the shower, he measured his steps carefully and quietly, making his way upstairs to his own distinctly chilly room. He did not want to alert the attention of Sherlock's bedmate, whoever he/she/it may be. Especially if they were as astute as the man himself, which was entirely possible, and even probable. He wouldn't deign to sleep with someone 'lesser' than himself, presumably.

Settling onto the bed with speed that was almost panicked, he unzipped and freed himself, gasping with relief. The January air was cool here, but he felt like he had brought a megaton of heat in with him...mostly generated by embarrassment and arousal.

He wrapped his fingers firmly around his ridiculously hard erection, casting a glance to make sure he'd shut the door. The last thing he needed was Sherlock hearing him. God, with that brain he would figure it all out too quickly - and John didn't know if he would be amused or dumbfounded by his flatmates' reaction.

John felt like he didn't know much of anything anymore, because Sherlock had just had what sounded like fantastic sex, which had turned him on to a painful degree, and that was just not a conversation to have. Instead he gave himself a long stroke, his breath hitching as heat knotted in the bottom of his stomach. Shit, but it was sexy though.

Brow furrowing into an oft-revisited visage of pleasure, he licked his lips once, a habit he had always had and one that he had so far failed to eradicate.

A few strokes told him that his body was in no mood to wait, it was primed to full and he was stunned to find he was already achingly close to a point of no return. He reactively shortened and sped his strokes, twisting swiftly and firmly, opening his indigo eyes to glance down with distracted fascination at the slickness he felt, his body's response to Sherlock's release.

He let out a long breath, careful to catch himself before it became a strangled moan, letting his fingers ghost over the tip of his cock to slick themselves before starting up his rhythm again. Normally he would take his time with this, twist his wrists and feel his way to orgasm - but he was already far too stimulated.

The whispers of Sherlock's moans echoed in his mind and his hand stuttered before redoubling its speed.

"Ah, ah...shit," he muttered, turning his head to his shoulder to keep himself quiet. At least he had some restraint.

He regulated his increasingly-staggered and coarse exhales as best he could, gritting his teeth against a sharp twinge of pleasure that almost hurt. Nibbling his bottom lip unconsciously, he dared to picture Sherlock in the throes of his climax.

God, what if someone could bring him to bliss like that? What if he could meet the challenge and take Sherlock there again, to that incredible, beautiful peak..? Oh - Shit, shit, shit!

He came quickly, and messily, and it was all over far too soon. Feeling underwhelmed, he lay there, cooling and drying off rather unpleasantly, listening to his heartbeat slow back down. It raced back up again when it occurred to him that he should really vacate the flat before Sherlock got out of the shower and bumped into him. The events would play themselves out on John's face like a HD movie with surround sound.

Trying to wet his lips with his dry tongue, John managed to fight off the languid urge to just lie there until he'd completely gotten his breath back, and forced himself into a sitting position. His heart was still fluttering in his chest, but it was starting to settle, even if the adrenaline was still trying to rack it up again.

He winced as he felt the little pool on his stomach get caught between his skin, pulling a face as he slipped off the bed and reached into his washing basket. He cleaned himself up, still feeling as though he hadn't quite scratched the itch, and desperately trying not to think about the fact he had essentially just got himself off solely on Sherlock's own orgasm.

Jesus, he thought, pulling up his jeans. He needed his head examined.