"I don't see why I have to be the sub," John grumbles. He tugs on the black wristband with a silver medallion wrapped around his wrist. "Besides, isn't there something about men that dominate in life secretly want to be dominated in bed? Not that I want any part of that, mind you. But still."

"Oh come now, John. I may be a good actor, but the idea that I could convincingly act the part of a submissive among a group of experienced Doms is absurd." Sherlock sniffs and brushes a speck of lint from his immaculately pressed black button up shirt. He looks devastating, and John's really, really trying not to be completely obvious. John looks down at his own shirt – a black muscle shirt artfully slashed across the front, showing glimpses of his chest when he moves. He feels utterly ridiculous. Trust Sherlock to get them involved in a blackmail and murder case that leads to private BDSM parties and way too much information about other people's sex lives.

Sherlock brings his wandering attention back to the matter at hand by a sharp tug on his hair. He starts to raise a protest before he remembers exactly what he's supposed to be doing. He sighs quietly and checks where he is; one step behind Sherlock, as he ought to be, either directly behind him or at least one shoulder behind him. He had no idea this whole thing came with so many bloody rules.

"Keep your head below mine," Sherlock had instructed. "Kneel when I sit, do not rise before I do, unless I ask you to. Don't speak unless spoken to. If you wish to tell me something, grasp my wrist. If you do speak, you will call me Sir."

"You're enjoying this entirely too much, you know."

"Not entirely. If you make a mistake, I'll have to punish you. In front of whomever happens to be there, probably. It would be…awkward. But I couldn't hesitate."

"Well, whatever you come up with, remember, paybacks are hell." John stands over Sherlock, almost between his knees, forcing Sherlock to tip his head all the way back to look up at him. "And I'm not your slave. So don't get used to it."

John did want to intimidate him, just a little bit, but was somewhat surprised to see Sherlock's reaction; dilated pupils and rapt attention, for a second, just a second, until Sherlock seemed to mentally shake himself. "Of course. I'll be…lenient."

John is both trying to remember all of his rules, and keeping an eye out for Piers Tanner, Master and blackmailer. Sherlock had learned that Tanner was well known in the BDSM scene, although his reputation for betraying those in his rather specific social circle wasn't. Sherlock hoped to engineer a little blackmail of his own, to draw him out, and learned he would be at the next play party. Which is where they are. A large house in the West End, with food and drinks and music downstairs, and "demonstrations" going on upstairs.

Demonstrations of what, exactly, John isn't sure. He's trying to not think about it too hard, as it's difficult enough to even be in this situation without picturing Sherlock as part of some sordid kinky sex scene. It's one thing to think of it while he's alone, quite another when Sherlock's sitting right there, so close John can feel the heat of him through his clothes.

He's kneeling rather uncomfortably next to the chair Sherlock has claimed near the bar, and since he's not supposed to talk, he tries to keep an eye out. There are throngs of people in the house, wandering through the rooms, chatting, socializing, separating and hooking up, ordering and following orders. John realizes that they're hardly outlandish here – there are plenty of same-sex couples, as well as hetero couples and even some groups. One man looks like he has a harem. John's musing about the logistics of keeping multiple women happy and satisfied, when he spots Tanner.

"Sherl-" he starts, and at Sherlock's sharp look, he clenches his teeth together. He reaches out and grabs his wrist, turns his head and nods toward Tanner's back making it's way up the stairs. Sherlock nods and rises from his chair, following Tanner up to the second floor.

…..

Molly drags the tip of her riding crop across Jason's back and down his thighs, flicking the small leather loop against his buttocks quickly, just a quick snap to keep him focused. Jason jumps a little at the crack, more a reaction to the sound than from any overt pain, Molly is sure, and turns her attention to her small, rapt audience.

"-so you see how easy it is to be lulled into a false sense of security with something like this. Small, lightweight, but incredibly flexible. You can tease – " Molly turns back to Jason and slides the end of the crop over his bound wrists and down his arms, across his chest and still lower, "-or warm – " small taps, nothing hard or sharp, patter their way across Jason's ass, and he trembles " – or chastise." Poor Jason stops moving completely, probably waiting for the blow to fall. "But I won't do that today, as Jason has been so delightfully good. What a gorgeous boy. Well done." Jason beams like he's just won the lottery. Molly reaches over to loosen the ties to the ropes when she spots someone familiar in the corner of the room. The one person that would be on the bottom of her list to meet up with in this particular place.

Sherlock Holmes.

Sherlock. Resplendent in black silk shirt and classic grey trousers, sleeves rolled up and collar opened, giving the entire look just the right amount bored nonchalance. His moon-bright eyes are currently trained on her in something like shock.

John Watson is with him, dressed in a ridiculous shirt, and by the expression on his face, has seen the whole thing and looks somewhere between stunned and ready to burst out laughing. Of course he recognizes her; it's not like she takes pains to disguise herself, not here, among friends. She looks at her black skinny jeans, spike heel boots, and purple halter and realizes that neither of them has probably seen her out of a lab coat before. She feels the first stirrings of panic start creeping up on her, then forces herself to snap out of it. This is her world, and damned if she'll let Sherlock bully her here, no matter how many times she's fantasized about it in private.

She quickly loosens Jason's bonds, leads him to the en suite bathroom, closes the door behind him and announces, "Thank you everyone. I'll be available later, if you have any questions." She pins Sherlock down with her eyes and points to the chair. He raises an eyebrow but doesn't say a single word, just waits for everyone to file out. Once the door closes, she rounds on them.

"What in hell are you doing here? And don't try to convince me it's for the same reasons I'm here, because that's a complete lie."

"Oh well done, Molly," Sherlock drawls, looking her over. "You're a switch. The rope burns on your wrists in February even managed to fool me. That's what I get for making assumptions, I suppose."

"Don't change the subject," she seethes, hand automatically rubbing her wrist at the memory. "Things got a bit out of hand. But still – why are you even here? Is this a case?"

"What makes you think so?"

Molly shakes her head. "Are you joking? You couldn't be more bloody obvious if you tried! Do you honestly think you can pass John off as your sub? Look at him, look at how he stands, how he walks! Christ, he doesn't even have a collar!" John lets out a gust of laughter and something that sounds like "I did tell you."

"Collars are utterly ridiculous. If a Dom can't mark his control without one, what kind of Master would he be?"

Molly cannot believe she's having this conversation, with him of all people. "Again, Sherlock, quit trying to change the subject. Is something going on? Because I can't imagine any other reason you'd turn up."

John decides he's had enough. "It looks like Piers Tanner is blackmailing some of the members here. He was here tonight, we thought we'd do a little work on our own to draw him out."

"Tanner? Oh Lord, what an absolute nutter. I'd never let him near me in restraints, that's for absolute certain. He's had a sub safeword on him four times in the last two months."

"Not learning, is he?" Sherlock asks.

"Apparently not," she says absently. "I think Vivian finally left him. I don't blame her." A little flare of suspicion is growing. Sherlock seems awfully knowledgeable, even somewhat casual about all of this. She eyes him carefully, but he simply looks back nonplussed, his eyes holding perhaps a glint of amusement, but not betraying it with his mouth. He turns toward the door.

"Well, Molly, this has been very illuminating. If you hear anything relevant, text me. I think it's time we reestablished ourselves, right John?"

John rolls his eyes and groans. He tries to school himself into his best "ready to serve," expression, fails utterly, then stalks toward the door, not even waiting for Sherlock. "I'm going down for a drink. I'll get you one. Pretend it's an order. I'll see you downstairs." He steps out, every inch of his self-pride showing in his bearing and gait. Molly chuckles. Even Sherlock has the sense to looks somewhat abashed.

"Yes, you're right. It's a miserable failure. I thought for an hour or so, but…" He turns to the door, and before Molly can stop herself, she lets her curiosity take hold. She simply has to know, and snaps her crop in front of Sherlock's shoulder to stop him walking. He stills immediately- obediently-and drops his chin to his chest. Heart pounding (Good God, when would she ever get this chance again), she moves the end up under his chin and uses it to lift his face until he's looking fully at her. She holds his eyes for a moment, until he dips his head and kisses the tip of her riding crop. "Thank you, Mistress," he murmurs, then winks and strides out of the door, Molly staring in openmouthed astonishment after him.

….

John takes a large mouthful of whiskey and wonders how to reclaim the stakeout, now that it's been rather upended after seeing Molly. He chuckles into his glass at the look on Sherlock's face after they opened the door to the demonstration. The sight of little, pale, mousy Molly Hooper wielding a riding crop on the bare ass of a well muscled man tied up to the ceiling is enough to keep John laughing for a week. He looks around, wondering where Sherlock has got to, when he sees him slice his way through the crowd, making his way to John's chair. He suppresses a sigh and prepares to slip off of the chair to kneel, when Sherlock surprises him and beats him to it, gracefully dropping to his knees next to John.

"I'm sorry I kept you waiting, sir," he says. John looks around, alarmed. Surely someone will have noticed the change in roles? It doesn't seem like anyone has, though, or if they do, it's something not completely out of the ordinary so they don't care. John tries to stamp out the rather lewd thoughts his brain insists on throwing at him at this turn of events and relaxes back in his chair. All he can see of Sherlock is his tall, proud back and the curve of his graceful neck.

"Have you seen Tanner?" John murmurs.

"No, sir. I've been reliably informed he's left."

"Damn. All for nothing then. Although – we did learn at least one thing tonight."

"Yes?"

"If you steal Molly's bone saw again, she just might crack you one on the knuckles and feel absolutely no fear. You've lost your advantage."

Sherlock huffs out a laugh. "She wasn't ever afraid of me to start with. Simply allowed her attraction to cloud her natural reactions."

"Yes, you're confounding, all right." John sighs, admiring the way Sherlock's bum rests on his heels, balanced and comfortable, like he has nowhere else to be. "I suppose we could go."

Sherlock doesn't answer, simply kneels there, unmoving.

"We're done here…so, let's be off then."

Sherlock's voice comes low and rough and tinged with amusement. "Is that an order?"

John's brain stutters, feeling power and arousal, and utter fear he might play this wrong. He decides to start somewhat jokingly, just to be absolutely certain, and leans forward to place a hand softly on the curve of one elegant shoulder.

"When we get home, the washing up will be done before tomorrow."

Not even the hint of a smile, or a twist of annoyance. "Yes, John."

"And that disgusting dead snake will be binned. You may keep the fangs." A little bolder, now.

"Yes, John."

He reaches up, brushes a finger along Sherlock's cheek, sweeping the curls away from his ear. He leans in , close enough to whisper without being overheard. "And when you're done, I expect you kneeling, naked, on my bed."

John sees Sherlock's chest hitch with a quickly drawn breath.

"Yes, John," he purrs.