Summary: Lestrade walks into a supposedly empty room at Bart's and finds something he did not expect. Even more surprising is his own reaction. Slash, John/Sherlock, future John/Sherlock/Lestrade, super smutty, rated M for a reason.

Disclaimer: I do not own these characters. They are the property of the BBC, and of course Arthur Conan Doyle. I do not make any profit from the creation of this story, except for getting myself all hot and bothered, which is probably not the kind of profit the BBC cares about.

Lestrade is walking down a corridor in the basement of St. Bart's in the middle of the night, on his way back to his office to complete some paperwork before finally going home after a very long day. The harsh fluorescent lights overhead glare down on him, stinging his eyes and painting bright stripes along the reflective linoleum floor. He is in the middle of dealing with a very challenging triple homicide, and he is exhausted. It does not help that he has had to ask Sherlock Holmes for help, yet again, and he has just gotten done dealing with Sherlock while examining a victim in the Bart's morgue. Sherlock swept in, full of arrogance and insults as usual, and blew all of Lestrade's nicely constructed theories out of the water in three minutes of observations. He and John then bickered for a few minutes before Sherlock swept out, leaving John behind to shrug sheepishly and mutter a half-hearted apology before rushing from the room to catch up with Sherlock.

Lestrade chuckles softly to himself as he thinks about the cocky detective and his loyal sidekick. He is annoyed with Sherlock's arrogance and frustrated to be proven so wrong, but he knows that he is lucky to have access to the detective's amazing skills and somewhere deep inside he is grateful for the help. He is also grateful for the presence of John Watson, who has had a stabilizing effect on Sherlock, whether he knows it or not. The way that they talk to each other, Lestrade has never seen anyone interact with Sherlock like that, so comfortable and easy and friendly. Relatively speaking, of course, as he does not believe that Sherlock can ever truly be easy with anyone. But nevertheless, it makes him happy to see it.

As he walks down the hall, lost in thoughts of this case, general musings about Sherlock and John, anticipation of the pleasure of going home and finally going to bed, Lestrade hears a loud, hollow bang come from behind a closed door just ahead of him. He stops, confused. He is sure that he is the only one on the floor at this time of night. Sherlock, John, and even Molly left ahead of him, as he stayed behind to make some notes about Sherlock's deductions while they were still fresh in his mind. As he stands there, he hears another bang, and a fainter noise that may have been a pained whimper. Still more confused than worried, Lestrade decides to investigate the sounds.

Lestrade opens the door, taking care to remain silent, listening for further sounds. He leaves the door slightly ajar behind him as he steps through. The door opens into a short narrow hallway that extends a few feet before widening to the right into a large room, possibly a classroom? A light is on somewhere in the room, out of sight, the soft incandescent glow a welcome contrast to the harsh glare of the fluorescent lights out in the corridor. It casts dim illumination down the short hall as Lestrade walks softly forward. He hears another muffled thump, along with a quiet grunting sound, and another quieter sound, faintly rhythmic, that he cannot place. Somewhat concerned, he steps around the corner, his eyes sweeping the room.

Shocked, he freezes where he is, standing just past the corner of the short hallway, barely into the room. The room contains several tables, the nearest of which is just in front of where he is standing. The soft light he noticed before is coming from a small lamp on a desk which is pushed up against one wall. Directly in front of him, the wall is lined with tall cupboards. And leaning up against these cupboards facing toward Lestrade is John, his head thrown back, mouth open, eyes squeezed shut, and hands splayed against the cupboard doors on either side of him. His trousers are open, pushed down his hips, and his hair is disheveled, sticking up in clumps and spikes. Kneeling in front of John is the familiar form of Sherlock, his back to Lestrade, deep blue silk shirt stretched taut across his form. His mop of dark curly hair is swaying gently as his head bobs up and down at John's waist. The room is filled with soft, wet, rhythmic sounds from Sherlock, and John's soft panting.

If Lestrade had thought about it before, had ever considered the details of a scenario such as this – and he hasn't, of course he hasn't – but if he had, he would have expected John to be the one on his knees. Sherlock is so domineering and aggressive in his interpersonal interactions that is makes sense to Lestrade that he would be the same in sexual matters. Especially with John, the faithful sidekick, always following along and doing Sherlock's bidding. But here he is, kneeling, while John pants above him. There is something about seeing Sherlock in this position that triggers something in the pit of Lestrade's stomach, a tight feeling that he cannot place. Lestrade feels the heat of embarrassment – just embarrassment, that's all it is – bring a blush to his face as he takes in the scene before him.

He needs to leave, he knows he needs to leave, just go and pretend this never happened, and he is starting to step backward into the protection of the little hallway when John opens his eyes.

Lestrade freezes again as their eyes meet. John tenses, closes his mouth and lowers his chin to look directly at Lestrade, eyes open wide in surprise. At his waist, Sherlock's head is still moving slowly forward and back, hands clenched on John's thighs. Lestrade looks back at John, eyes wide, his blush intensifying, and shakes his head softly, just the barest motion side to side, trying to apologize without making a sound. His breath is coming faster now, his chest rising and falling visibly. He needs to go, right now, and again he tries to step back, out of sight of the two men and this personal act. He lifts one foot to step backward, but finds that he cannot complete the step. He lowers his foot, and succeeds only in rocking back and forth in place, still facing the two men, looking helplessly at John.

John's eyes narrow as he watches Lestrade's hesitation, takes in the blush and the rise and fall of Lestrade's chest. His mouth curls in a small smile, and he allows his head to fall back against the cupboards again, still looking directly at Lestrade through suddenly hooded eyes. His smile widens, and as Lestrade watches, John slowly licks his lips, first the top and then the bottom. Lestrade's mouth falls open and he feels his knees weaken, that tight feeling in his stomach intensifying. Somehow, the smile that John is wearing – small, quiet, unassuming John – that smile is the most lascivious thing Lestrade has ever seen. He feels himself starting to get hard, and he should be shocked at himself, shocked yet again, but somehow he is not. Still he does not leave, just stands in place, silently staring back at John.

They continue to lock eyes as Sherlock slides his mouth up and down along John's cock, the slow, changing rhythm in the movements and angle of his head suggesting to Lestrade that he has some skill at this. John opens his mouth again, panting louder now, his eyes fluttering closed briefly and then opening, always looking back at Lestrade, smile still in place. Time stretches out, fifteen seconds, thirty, as they continue to look at each other. And Lestrade knows that he should still leave, should have left some time ago, that his staying here and watching this is crossing some line that he did not even know existed until he entered this room. But he does not leave.

After some undefined interval, the wet rhythm of sucking sounds the only thing to mark the passage of time, John smiles wider, and Lestrade somehow knows that he has reached some kind of decision. Before he has a chance to wonder what it is, John lifts his left hand from where it is braced against the cupboards and threads his fingers through Sherlock's messy curls. Eyes on Lestrade's face, he works his fingers deep into Sherlock's hair, winding the curls around and between his fingers. Then, suddenly, he tightens his grip, clenching his fingers tight. Lestrade can see Sherlock's head jerk at the sudden force, but he continues to move up and down. A low baritone moan floats out into the room. Lestrade realizes suddenly that it is coming from Sherlock, that he is moaning as John pulls his hair while he sucks John's cock, and immediately Lestrade is flooded with intense arousal, the sensation slamming through him with such force that his knees buckle and he lurches forward, barely catching himself on the table in front of him. He manages to do so without making a sound, and stays in that position, braced on his hands leaning forward over the table, staring back at John. His cock is rock hard, straining against his trousers. He starts panting in earnest now, opening his mouth wider so that his breathing stays silent. He is sure, somehow, that if he makes a sound, this will stop. And all at once he very badly does not want this to stop.

John is still looking at Lestrade, maintaining eye contact, as he starts to use his grip in Sherlock's hair to pull his head more swiftly back and forth. Sherlock moans again, his neck flexing, allowing John to control his rhythm and speed. Lestrade watches, mouth open, as John roughly pulls Sherlock's hair, forcing the detective's head to move faster and faster on John's cock. The sound of his sucking gets faster and louder, less controlled. John glances down at Sherlock, and then looks back up, meeting Lestrade's gaze. John licks his lips once more, and then…

"Oh yes, Sherlock," John groans, eyes still locked on Lestrade. In response, Sherlock grunts out another deep moan. Lestrade feels hot sparks of pleasure shoot through his spine at the sounds, both at John's words and Sherlock's inarticulate, needy reply. His stomach pulls tight and he shivers, watching John's face. John continues to pull Sherlock's head forcefully up and down on his cock, fingers twined tightly in his hair, continues to hold Lestrade's gaze.

"Sherlock, yes, you feel so good. I love how your mouth feels on my cock." John's voice is lower, deeper than Lestrade has ever heard it. His eyes, staring straight into Lestrade's, are dark with desire. If Lestrade had ever thought about it before, ever considered how John and Sherlock would talk dirty – and he certainly hasn't, absolutely not – but if he had, he would have expected Sherlock to do the talking. Sherlock's deep voice seems made for talking dirty, for describing in detail each and every sexual act in a rumbling baritone. On the other hand, Lestrade supposes, it is possible that Sherlock would not be good at talking dirty. He briefly imagines Sherlock listing off the scientific names for body parts and describing the chemical reactions responsible for arousal using the same tone and pace he uses to explain his deductions, and feels a fleeting and extremely inappropriate urge to laugh, before John's voice recalls his attention to the scene unfolding in front of him and the sharp spikes of arousal coursing through his own body.

"Mmmm, yeah, like that. I love to fuck your mouth." Lestrade sags onto his hands, leaning his hips up against the table as his muscles go weak. Hearing John using such vulgar language while looking directly at his face causes another surge of arousal to stab through Lestrade, rippling up his spine and sending pulses of pleasure along the muscles of his shoulders and neck. Sherlock is moaning steadily as John talks, gripping John's thighs to brace himself as John continues to force his head forward and back.

"I love to see you on your knees in front of me, love to watch my cock sliding in and out of your gorgeous mouth." John's eyes flick briefly down to Sherlock as he says this, but almost immediately come back up to lock with Lestrade's. "It's like you were made for it, made to suck my cock." Sherlock grunts frantically in response to this, a clear affirmative.

John brings his right hand up and gently cups the side of Sherlock's face, his touch light and caressing. His left hand tightens still further in Sherlock's hair, and he pulls Sherlock's head back, away from his cock. From his vantage point, Lestrade can see nothing explicit, but he imagines that John has pulled Sherlock nearly off his cock entirely, possibly just the very tip still between his lips. John holds his head there, keeping Sherlock in place with a vicious yank to his hair, as Sherlock whimpers and writhes and struggles to get his mouth back around John's cock. Again John breaks his eye contact with Lestrade to look down at Sherlock, as Sherlock looks up at John. Lestrade finds himself picturing how Sherlock must look in this moment, lips swollen from the friction of his sucking, pleading expression in his eyes as he silently begs to be allowed to continue sucking cock. John smiles again as he looks down at Sherlock, this smile somehow more predatory and salacious even than the smile John gave him earlier.

"What do you want, Sherlock?" John asks in a low, dangerous voice. Lestrade leans forward, listening for an answer, but does not hear one. John leans his head back, smile still in place, and immediately meets Lestrade's eyes once again. He waits silently, keeping his brutal grip in Sherlock's hair. In front of him, Sherlock is struggling to lean forward, his hands clenched tightly on John's thighs, moans and whimpers continuing to pour from his throat. John just waits, still silent, tugging fiercely on Sherlock's hair when his struggles get too boisterous.

Eventually, Sherlock stops struggling and falls still, whimpering quietly. John softly caresses his face with the hand that is not twisted in Sherlock's hair. Eyes still locked with Lestrade's, John says "Sherlock, shhhhh." His voice is still low, but softer somehow, almost tender. "Tell me what you want, Sherlock. Tell me what you want ... and I'll give it to you." For some reason, Lestrade feels like this last statement was not directed solely at Sherlock, but he does not want to think about it now.

Sherlock freezes entirely and falls silent, still looking up at John. Lestrade leans forward and holds his breath, desperate to hear Sherlock's answer. For a long moment there is silence, and then Sherlock responds, his rich baritone voice somehow breathy and desperate.

"I want you, John. I want your cock, I want to feel you, feel you in my mouth, feel your cock sliding back and forth across my tongue and my lips. I want you to fuck my mouth, use me for your pleasure, come down my throat. Please, John."

Lestrade cannot move, literally cannot move as he listens to this. Arousal, fierce hot raw desire, is pulsing through his body. His hips start rocking softly, thrusting his aching cock forward and back against nothing, and for a moment he thinks he might come in his pants without ever being touched. In front of him, John watches him for a moment, and then looks back down to Sherlock. He pulls both hands around to cup Sherlock's face tenderly, and then moves both of his hands into Sherlock's hair, gripping tightly on both sides of his head. He looks back to Lestrade once again, and without warning slams his hips forward, thrusting the entire length of his cock into Sherlock's panting mouth. Holding Sherlock's head stationary with the grip in his hair, John starts to fuck Sherlock's face in earnest, snapping his hips forward and back with brutal speed. Sherlock moans, shockingly loud, and his hands fall away from John's thighs, coming to rest limply on the floor on either side of his own spread thighs where he is kneeling back on his heels. He simply holds himself still and allows John to fuck his face, grunting and moaning out his pleasure.

John is grunting through his teeth as he continues to pump his hips forward and back, hands twisted in Sherlock's dark hair. His eyes keep fluttering closed, but each time he opens them again he is still looking at Lestrade. And Lestrade is looking back, staring at John's face, unconsciously rolling his hips in the same rhythm that John is using to fuck Sherlock's mouth. Lestrade is panting aloud now, simply cannot help it as waves of pleasure and arousal wash through his body, but the sound of his labored breathing is swallowed up by Sherlock's increasingly fevered moans and John's rhythmic grunts.

"So ... good ... Sherlock," John gasps out. He throws his head back, throat working as he swallows repeatedly, clearly trying to get control of himself. He brings his chin back down and looks into Lestrade's eyes, bites his lower lip. Lestrade mirrors the action, teeth sinking in nearly hard enough to draw blood. The twinge of pain he feels just adds to his arousal, and he is not sure if he has ever been this hard.

"God, you look so good, feel so good. I just want to fuck your mouth all the time, forever. I want to tie you up, hands behind your back, naked and kneeling by my bed, and use you whenever I want. Just push my cock in your mouth and fuck your face any time, just take what I want, whenever I want, without even asking you. Would you like that, Sherlock? Would you like to be my fuck toy, my cock whore?" And Sherlock is groaning, nearly squealing, around the cock in his mouth as John talks, his back flexing beneath the tight blue silk as he rolls his hips. Lestrade pictures the scene as John speaks, thinks about himself using Sherlock in this way, or even being used himself, and feels arousal pooling low in his stomach, electric sparks of heat and pleasure crackling up and down his spine. He grits his teeth to stop himself from whimpering out loud, watches as John's eyes flutter closed again and then open, piercing gaze freezing him in place.

"Touch yourself."

For a moment, one crazy moment, Lestrade is sure that John is talking to him. He draws in a sharp, startled breath, pulling his head up to look John full in the face. His fingers clench against the edge of the table where he is leaning, and his hips still in anticipation. Then he sees Sherlock's hands coming up, moving around to his own groin, working frantically to open his trousers. Lestrade draws another deep breath, feeling both relieved and somehow disappointed when he realizes that of course, of course John was talking to Sherlock. In the next second he forgets his disappointment, forgets himself entirely as he watches Sherlock, arm working feverishly as he rapidly strokes and pulls on his own cock while John holds his head in place and fucks his mouth. Sherlock's back is flexing and bending as he moves his hips in time with his hand, and Lestrade can see the shadow of his spine through the tight slick fabric of his shirt as he moves.

The room is filled with the sounds of grunting and moaning, obscene slurping and wet rhythmic slapping noises, harsh labored panting. Lestrade is gritting his teeth against the sensations coursing through his body as he watches the scene unfolding in front of him, and again he thinks he might come. John's eyes continue to bore into his even as John's breathing and thrusting start to get erratic as his climax approaches. Below him, Sherlock's arm is still moving frantically, his hips jerking and rolling faster and faster.

Suddenly John tightens his grip in Sherlock's hair and snaps his hips forward, freezing in place with his cock buried as deep as it can go in Sherlock's mouth. He remains motionless, pushing himself hard into Sherlock's throat. At his feet, Sherlock writhes and bucks, and the hand at his waist actually speeds up. Sherlock is making short, sharp, desperate little grunts as John's cock blocks his airway almost entirely. Lestrade feels the muscles of his back clench up as he watches, freezing in place as John does, his own cock twitching in his pants, staring as Sherlock comes completely undone.

"Take it, Sherlock, take my cock all the way down your throat. Can you feel it, pressing against your lips, your tongue, the roof of your mouth, your cheeks, your throat? I can feel every part of your mouth around me, feels so good. So good," John groans out, voice deep and guttural with arousal. Sherlock is grunting faintly around John's cock, head held stationary between John's hands as the rest of his body jerks and contorts at John's feet, hips snapping back and forth as he works his cock. Lestrade feels his arousal heighten even more as he watches Sherlock lose control on his knees in front of John. And then, impossibly, John pushes his cock further into Sherlock's mouth. Sherlock's little grunts get fainter and higher as John pushes slowly forward into his throat until he falls completely silent, his airway entirely filled. Lestrade can see his throat convulsing around John's cock, stretching and hollowing out as his lungs strain to breathe. Sherlock's hips curl up and forward, rounding out his spine, and he stops moving. John flicks his eyes down to Sherlock's still form, and then back up to Lestrade's face.

"Come for me. Now."

And Sherlock does. His arm pumps up and down at his waist and his hips snap sharply backward and forward once, twice, three times as he comes silently, John's cock still buried in his throat. Lestrade sags forward against the table, silently mouthing the words "sweet Jesus" as he watches Sherlock coming at John's feet. Suddenly, John pulls his cock almost all the way out of Sherlock's mouth. Sherlock immediately draws in one harsh, ragged, shrieking breath and surges his head forward, capturing John's cock once again, hips snapping back and forth erratically as he rides out the rest of his climax. And Lestrade cannot help it, simply cannot help himself. He brings one hand to the front of his trousers and presses on his aching cock, thrusting forward and rutting against his own hand. Two thrusts and he is coming too, working to keep silent as the waves of pleasure course through him, John's eyes still on his face. He is not able to keep entirely silent this time though, and a rough choking grunt escapes his mouth as he nearly collapses on the table top in front of him.

"Oh God, yes!" John nearly shouts, staring hungrily as Lestrade comes in his pants. John clenches his hands tighter in Sherlock's hair and pulls his head roughly back and forth, humping Sherlock's face and moaning loudly. Lestrade leans against the table, panting, riding out his own aftershocks, as John starts to come in Sherlock's mouth. Sherlock moans loudly again, slurping and swallowing as John shoots down his throat. John slams his head back against the cupboard with a hollow bang, his eyes squeezed tightly shut, mouth open and panting harshly, still thrusting into Sherlock's mouth as he comes.

And all at once, Lestrade thinks about where he is, what he is doing. He stands quickly, looking down at the floor, mortification flooding through him as quickly as arousal had done before, bringing a deep red blush to his face. His pants are sticking to him uncomfortably, and the cold wet feeling just adds to his embarrassment. Backing away quickly, he turns and flees the room without another glance at the now spent couple.

A/N: So there you go. This is the first installment of a longer story, so if you enjoyed it, please stay tuned. I don't know how often I'll be updating, but I'm pretty driven to get this written right now, so hopefully soon. This is my first published fic ever, so I would really appreciate reviews and constructive criticism. I'm having a fantastic time working on this, hope you like it as much as I do!