Written as an exercise to get me back into writing so that I would finish 'Someone That I Used To Know', but it got a little out of hand.

Based on a prompt given to me by the lovely Dvancecinco, 'Sherlock comes home one day to discover John has… '

Un-beta'd. All mistakes are my own, feel free to point any out to me.

It was gone midnight when Sherlock walked through the doorway of 221 for the first time in three days. He moved down the entryway and towards the stairs with an uncharacteristic lethargy. One of the few things in the world that could drain Sherlock of his energy stores at an alarmingly efficient rate was extended exposure to his family. If Mycroft's incessant political drivel wasn't mind-numbing enough, his Mother's constant bemoaning of a lack of Grandchildren and regular visitations from her sons was what would push Sherlock beyond his limit. All but trudging up the stairs to his flat, he unexpectedly realised how nice it would be to collapse into bed and sleep for a few hours. John must never know the effect his family have on him, Sherlock thought, otherwise he might insist on weekly visits just to make sure the detective got at least semi-regular sleep.

His mind occupied with the thought of soft pillows and a downy duvet, it wasn't until he reached the first landing that Sherlock heard the noises emanating from the living room.

It was unquestionably John's voice, pitched low and sounding as if he were out of breath. If the door leading from the first floor landing to the kitchen hadn't have been open, Sherlock may not have heard anything until he was already in the flat.

He approached the open doorway silently, listening for signs of distress. But, as it rapidly became clear, they were not those kinds of noises. And suddenly, Sherlock was no longer tired.

The noises John was making were not words of any form, just moans and throaty growls, sometimes inter-spliced with a sharp 'ah' sound. Underneath his flatmate's voice, Sherlock could hear the creaking of the leather sofa and the shifting of fabric.

Whilst keeping his ears trained on what was occurring in the lounge, Sherlock stepped into the kitchen and scanned his eyes over the evidence. Judging from the way the chair nearest to him had been knocked into the table causing the salt shaker to topple over, the door had been left open because those entering through it had been otherwise occupied in one another. John's jacket lying in a pile on the floor behind his armchair was further testament to this. The two of them had obviously moved unseeing towards the sofa, removing clothing as they went and subsequently knocking into the odd piece of furniture. Odd that they should choose to retire to the sofa instead of John's... Ah, Sherlock thought. Yes, he was home early. He had intended to return in the morning - well, later in the morning - and had deemed it unnecessary to inform John of his earlier than scheduled departure. John must have thought he was safe for the time being.

So John had brought someone home and was having sex in the living room unaware that his suddenly-not-tired flatmate was listening.

Forget about it and go to bed, called a voice in the back of Sherlock's head that sounded suspiciously like his otherwise-engaged friend in the next room.

Unfortunately, a loud voice that sounded much like his own blared like a tannoy and reverberated off the wall of his skull as it chanted, 'observe!'

Never one to resist his own advice, Sherlock edged towards the partition between the kitchen and the living room and stood with his head and left shoulder just over the threshold so that he had a clear view of the sofa.

The sight that greeted him confirmed several facts; some unspectacular, some utterly surprising.

Of the unspectacular were: confirmation that Sherlock had correctly surmised from the sounds he had caught that the act in progress was fellatio (with John obviously as the receiver); John had left late in the evening to go out and was therefore not particularly drunk; and the plant Sherlock had left on the far windowsill had wilted almost entirely, proving that Mr Richter was innocent.

The surprising facts however were naturally of far greater interest to the detective. Of chief interest was that the person knelt on the floor between John's legs was not a buxom young woman, as was John's usual taste, but rather the figure of a lean young man. Sherlock couldn't see the man's face, but he judged him to be in his early thirties at the latest, obviously with a taste for running looking at the musculature visible under his tight t-shirt.

Within this surprise lay other surprises, such as the fact that John had kept such a thing as his less-than-heterosexual sexuality from Sherlock, that Sherlock had simply taken John at face value and never extrapolated such a piece of information. And that the sight of John, head flung back, neck arched, groaning throatily and fully dressed but for his dick in the other man's mouth, would send a spark down Sherlock's core and make him twitch in his underwear.

Yes, he was very much the opposite of tired by now.

The stranger's head bobbed in John's lap, not rapidly, but rhythmically. John's legs were spread wide on either side of his partner and his hands were running through the wavy brown hair atop the head that moved over his crotch. His mouth hung open slightly and every few seconds that insatiable tongue would flick out to wet a lip or poke at the corner of one.

Sherlock had unconsciously stepped fully into the room. He was captivated by the stream of information before him. He had thought, in regards to the man's sexual preferences at least, that he had John Watson sussed. Yet here was his friend, with a man between his legs, looking blissfully content and very much confident in the arrangement. It pleased Sherlock in the most undefinable way to be wrong about John once again.

Of course John's unwitting exhibitionism ended abruptly when he lowered his head from the back of the sofa to admire his companion's work and instead locked eyes with his flatmate who was stood at the other end of the room with surprised look on his face.

The shock caused the doctor to exclaim 'Oh God!' in a completely non-sexual way and jerk his entire body, which in turn caused the man at his feet to choke on the cock that had just been thrust into the back of his throat.

Whilst the two men hurriedly disengaged and attempted to hide their embarrassment by righting their clothing, Sherlock straightened his back, clamped his jaw which had unwillingly dropped and waited for the air to settle.

John's runner friend promptly left, leaving promises of a phone call he never intended to make in his wake. John, still on the sofa, threw apologies at the open doorway before agitatedly running a hand through his hair.

Twitching with a mixture of nervous energy and embarrassment, he said, 'You're back early.'

Sherlock hummed and began walking towards the sofa. John hadn't looked at him since that moment of discovery and Sherlock found that he very much needed to look into his eyes just for a second, just to determine how what he wanted to do would be received.

Predictably, John's nerves began to give way to anger. He frowned and pointedly asked the spot in which Sherlock had been a standing a moment previous, 'Just what the hell were you doing standing there anyway?'

Still no eye contact, so Sherlock moved closer until his shins hit the edge of the couch. At this, John looked up at him. Sherlock knelt on the edge of the sofa, his left knee between John's, his right by John's left hip. The frown on John's face had gone and he was looking at Sherlock with open curiosity.

What Sherlock had felt when he had stepped into that room, what he was feeling as he knelt over John, was not new. He knew lust when he felt it. He'd felt it before, acted on it before, and he wanted to act on it now. And when Sherlock wanted something, he went for it, so he leaned down until his face was less than an inch from John's, his head angled so that their open mouths aligned but did not touch.

John's breath stuck in his throat the moment Sherlock's lips stopped to hover over his own. It was all the confirmation Sherlock needed.

They looked at one another and in almost a whisper Sherlock said, 'You didn't finish', before he slid his left hand down John's stomach, over his belt and to the front of his jeans where he pressed the heel of said hand against the not-quite-gone hardness beneath.

John's halted breath rushed out of him at that and his eyelids flickered. Sherlock gazed down at his own hand as he pulled down John's zip and slipped his fingers inside, drawing John through the gap in the front of his boxers. Still focussing on his movements, Sherlock began to stroke John back to full hardness. John's breathing became ragged, dragging out a quiet whine every now and again when Sherlock would twist his hand around the head of John's cock.

Before long, John's hips were twitching with every up stroke. Sherlock's own erection was straining against the confines of his garments and he too was shifting his hips in time with the movements of his hand to try and gain any kind of relieving friction.

Noticing Sherlock's discomfort, John raised his eyes to that of his friend's, whose face was still but an inch away. Gazes locked once again, John dragged his previously limp left hand up the inside of Sherlock's right thigh and cupped the bulge at the juncture of his legs. It was Sherlock's turn to moan.

John wasted no time in extracting Sherlock from his trousers and pants and soon they were stroking one another in unison, Sherlock still kneeling over his friend.

As their respectively string-roughened and gun-calloused hands rubbed pleasure into one another, Sherlock and John's open mouths shared panting breaths. Their lips ghosted over that of the others', sometimes touching in fleeting moments, never quite kissing. Soon their breaths became vocal and they could each feel the stiffening of muscles in the other as their climaxes grew near.

John's free hand grasped Sherlock's waist, whilst Sherlock's clutched at John's nape. The circuit of their connected bodies transmitted the intimacy of what they were doing, something that had been missing earlier with the stranger. This wasn't mindless sex, Sherlock realised. This was just the next natural step for them in their ever changing relationship.

John's rhythm suddenly wavered and his deep moans grew higher. Sherlock, unable to speak, rubbed the tip of his nose against John's in encouragement until John understood and increased the speed of his hand so that both men were perched on the tip of orgasm.

John, having been stimulated for longer than Sherlock, came first with a cry of ecstasy, his release spreading up Sherlock's thigh that still rested between John's. His trailing whimpers, high pitched and breathless, landed in Sherlock's open mouth and travelled down the length of the detective's body, catching like a spark in his gut and made his orgasm catch fire. He scratched his nails against the back of John's neck as his muscles contracted and he came for what briefly felt like eternity.

Sherlock slumped down and sat on John's thigh as they came down from their high, noses still touching, hands still clutching.

Eventually, Sherlock faintly registered John wiping off the mess with a tissue that he must have had in his pocket. He tucked himself away and slid off his friend's thigh to sit beside him on the couch. The growing silence was in danger of becoming horribly awkward so Sherlock let his head fall to the side and rest on John's shoulder. John chuckled before rubbing his cheek against Sherlock's curls.

'I'm glad you're back early', John mumbled. Sherlock smiled and couldn't help but agree, however he found himself far too tired to say as much. So he closed his eyes and vowed to write his Mother and Mycroft a thank you letter in the morning.