The third time was totally deserved.
"Can't you play something more . . . tonal?"
Sherlock twisted his torso as he played, just enough to shoot John a peeved look over his shoulder. "I'm not in the mood for tonal."
"We just finished a case an hour ago!"
"And it was boring." Sherlock drew the bow sharply across the strings, producing another harsh screech. "I don't know why Lestrade bothered to call us in - it was a clear suicide. Even the Yard could see that."
"You spent an hour interviewing the other staff."
"Yes, because I was bored. Wanted to see if I could concoct at least a half-plausible scenario to fool everyone with. But it was pathetically obvious from the start that she poisoned herself on purpose, no mystery to that. Boring." He forewent the bow altogether for a vivace pizzicato cadenza, a near-random assault of plucked notes with only a hint of musicality behind them.
"You bloody well kissed the upstairs maid," John hissed.
"Not that it did any good; she was as clueless as all the rest. Honestly, John, what's the point of all this anyway? I might as well be back on cocaine."
"Don't you fucking dare." John growled. "You know you've got the ability to forfeit this little wager any time you feel like it - don't blame me if you're in a strop."
Sherlock grumbled something unintelligible and doubled the volume of his cacophonic scrabbling.
And John suddenly felt like it was the most natural thing in the world to stand up, wander over to stand behind his flatmate, and plunge his hands into Sherlock's back pockets.
Sherlock stiffened, the bow falling away from the strings with a scraped whisper.
"Keep playing," John murmured in his ear. "If you stop, I stop."
"What-"
"Do it." John punctuated the command with a bit of a squeeze, cupping Sherlock's delectable arse through the thin fabric lining the trouser pockets. "You're bored, so I'm going to endeavor to be interesting."
"Oh," breathed Sherlock in a small voice. He had to take a moment to suck in a breath - a moment in which John tightened his grip again and had a moment of what the fuck is my life seriously because damn - and then put the bow to the strings again in some semblance of a tune.
It was permission. John didn't even bother trying to hide what he was sure was probably a predatory expression - he was behind Sherlock's back anyway. He shuffled closer, close enough for the noticeable bulge in his own trousers to just barely brush Sherlock's arse, and slowly brought his hands around to hover over his flatmate's hips.
"You don't even realize, do you." It was a statement of fact. "You were kissing that maid today in the pantry like some sort of regency rake, and she had her eyes closed, but you were watching me. I did notice. Were you thinking of kissing me, then? Wondering what my mouth tastes like? Or were you just that desperate to get off?"
"John-"
"Hush." John slid his hands around the rest of the way, tugging Sherlock's shirt up just enough to insinuate his palms underneath, flat against Sherlock's taut abdomen, then pulled Sherlock backward with a steady pressure until they were flush against each other from shoulders to thighs. "Keep playing. If you stop, I stop."
The melody from the violin turned plaintive.
It was as close to explicit consent as they were likely to get, and John took a moment to just relish the feel of Sherlock's body against his own. Comfortably warm, all long angles and sharp corners, but lithe and graceful for all that. Sherlock stood perfectly still except for his bowing arm, his elbow gently rocking back and forth as he drew more notes out of his instrument. John didn't have to look to see that Sherlock's eyes would be closed. Waiting.
Sherlock's abdomen tensed slightly under John's palms as he slid them downwards. He had to work by feel, unbuttoning Sherlock's trousers and opening the flies, but there was a tantalizing tickle of body hair against the backs of his knuckles the lower he went on Sherlock's stomach and finally he had the trousers open and free access to the boxers underneath. Probably just some normal cotton not-at-all-sexy pants, but John couldn't see and was therefore free to imagine whatever he wanted. Red, perhaps? No, purple - royal purple, the same shade as that ridiculously sexy shirt Sherlock wore sometimes.
Not that the shirt Sherlock had on now was all that terrible. A plain black button-down, open at the throat, a triangle of pale skin visible if only John were in a better position to see-
Yeah, fuck that. John palmed Sherlock's cock, just gently shifting up and down with infinitely light strokes, but he brought his other hand up to Sherlock's throat and started teasing the buttons free one-handed. Sherlock made a strangled noise, almost a whimper, but he didn't actually speak. Instead, the plaintive melody grew more intense, darker, more haunting. He was communicating through music instead of relying on mere words and it was just about the sexiest fucking thing John could imagine. The rest of the buttons came free quickly, one right after another, and then Sherlock's shirt was hanging loose at his shoulders and John could touch anywhere he wanted.
Which he took advantage of. Ruthlessly. Sherlock did let out a bit of a squeak when John pinched his right nipple - gently, but firmly - but John slipped his other hand through the slit in the boxers to wrap around Sherlock's warm cock and the squeak melted away into a sigh and a long glissando of high notes. Absolutely bloody beautiful.
"You probably don't need me to tell you how amazingly sexy you are right now," John whispered into the hollow between Sherlock's shoulderblades. "I don't even need to be able to see to know what you'll look like - you've got your blissed-out face on at the moment, I can tell. You keep arching back as you play, exposing that long neck of yours, and I just want to suck a nice big mark onto it, right where everyone could see. You'd have to hide out here for days."
Sherlock moaned, the low sound an actual physical vibration from his chest cavity straight through to John's lips at his back. John tightened his hand around Sherlock's cock, one firm squeeze and a stroke, then back to the gentle caresses.
"Think you could come like this?" he pressed. "My hand on your cock, slow and steady? Not even really moving, just . . . touching? I bet you could. I bet you'd freeze up and your melody would falter and you'd shiver as you came. I could press up against you like this -" - he fitted himself to Sherlock's back, his hard cock pressing into the cleft of Sherlock's arse - "- and I'd feel your whole body just fucking come apart. Would it be worth losing the wager, do you think? Do you want to come?"
"John - please!"
"Please stop, or please don't?"
"Mmmmph." Sherlock arched his back, grinding against John's erection, but he seemed to be beyond anything except for groans and the instinctive slow spray of notes issuing forth from his fingertips.
"Tell me."
Another little hitch. "I'm going to come, John," Sherlock gasped. "I'm almost there - oh please -"
"Not yet, you don't." John tightened his grip on the base of Sherlock's shaft, squeezing his bollocks firmly and withdrawing his other hand altogether, wringing a despairing cry from his flatmate. "Not for another week. Writhe and moan and beg all you like - all you're doing is making it better for me." He reached down with his free hand and unbuttoned his own flies, dropping his trousers and pants down to his knees with practiced ease. "How about me - think I can come like this? I've barely touched myself, you know. And yet I'm so fucking hard I can't see straight, because I've got you desperate like this." He flexed his hips slowly and carefully, his cock nudging against Sherlock's arse through the material of Sherlock's trousers and pants.
"Yes." Sherlock arm dropped suddenly, the music cutting off in the middle of an arpeggio.
"Hey." John sank his teeth into Sherlock's shoulderblade - not hard enough to hurt, not enough to break the skin, but definitely hard enough to get his attention. "You stop, I stop. That was the rule."
Sherlock hastily brought the bow back up to the strings and started sawing away as if his life depended on it, tonality and rhythm be damned.
Like that - with Sherlock shifting and grinding slightly against him as he played, with one hand clenched immobile around Sherlock's cock and the other frantically pumping his own - it didn't take long at all. John closed his eyes, listened to the way Sherlock was desperately drawing long strings of jumbled notes from the violin, felt the way Sherlock was hot and heavy and hard against his palm, and then he was shivering his way through a spine-tingling orgasm and his cock was painting the small of Sherlock's back with stripes of come. John gasped and panted and had to lean forward and drape himself against his flatmate's bony shoulders for balance for a long minute afterward. The notes slowed, transformed back into an actual melody, then slowed further until they were just a gentle musical whisper in the otherwise-silent room.
"Bloody hell," John breathed.
Sherlock's only answer was a long, low hum.
"Last chance to change your mind?" John was pretty sure Sherlock was enjoying their little wager, despite his current state, but it was only polite to check-
"New rule," Sherlock murmured, his tone uneven. "When I win this wager, I get to be inside you when I finally get to come. If you don't kill me with blue balls first."
"That's . . ." John eyed Sherlock's ruined shirt with a primal sense of satisfaction. Gorgeous. "Yeah, I suppose we could amend the wager, if you like. I'm probably going to keep cheating, though."
Sherlock dropped the violin down to his side and let his head sag forward, taking several deep breaths. John stayed right where he was, standing close enough to touch but without actually touching, letting Sherlock regain his composure. "All right," Sherlock finally said. "Fine. Good."
"Good," John echoed. And then - on impulse - reached forward and ran a single finger through the messy spot at the small of Sherlock's back. "You were begging to lick this off me last time, you know," he murmured. "Might not be able to reach it back here, but I certainly left you as much as you want."
Sherlock stayed there, immobile and silent, while John escaped to his room.