A/N: Written for the tumblr prompt: give Sherlock's dance lesson a different (romantic) ending. Hope I don't disappoint. Will be updating soon.

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It's an unseasonably warm afternoon and the three of them are in Sherlock's sitting room, sifting through stacks of invitations, seating arrangements, and other such documents relevant to planning a wedding. They've been like this for the greater part of two hours and Sherlock's neck is beginning to ache, a dull twinge beginning just between his shoulder blades and working its way up toward the base of his skull. He gives his trapezius muscle an experimental prod and winces at the sudden jolt of pain.

Wedding planning is immensely tedious, in ways he never cared to find out. There are seemingly thousands of tasks to accomplish before the big day itself, and John is constantly on edge, snapping at everyone in the vicinity for even the most minor offenses— Sherlock's scarf left on the floor; Mary forgetting to steep their tea long enough. It's a lot to manage, but John has admittedly always held up well under pressure. This behaviour is out of character. Sherlock keeps wondering if maybe it's because this is different. This is a wedding, marriage. A permanent change. John believes it is going to be the most important day of his life, he said so when asking Sherlock to be his best man several weeks earlier. So perhaps this is simply his natural reaction in the face of something so apparently significant.

There are—other—potential reasons he might be acting this way, but Sherlock has already marked this as dangerous territory, and tugs his mind away from those avenues of thought, blinking down at the phone number for a local patisserie in his hand with mingled irritation and misery until remembering that he was supposed to call them and inquire about the price of wedding cakes. He exhales sharply and lifts the phone to his ear.

On his left, Mary is scribbling names of guests on a sheet of torn newsprint. Her brow is furrowed with concentration and the tip of her tongue is evident between her lips, smudging the carefully applied cherry lipstick she wears on Wednesdays. The collar of her shirt is rumpled, turned partially inside out, and Sherlock experiences a bizarre wave of satisfaction at the sight. Stupid. He swallows and pulls his mouth into something more reminiscent of a smile. Mary glances up and catches his eye, winking, then rolls her eyes at the telephone.

"It's the worst, isn't it, being put on hold."

"Dreadful," Sherlock agrees companionably, switching the phone to his other hand while reaching for a cooling mug of tea.

"If they're going to make you sit there for ages and waste time, they could at least play better music." She wrinkles her nose as strains of Where the Party At flow from the receiver.

"Indeed."

By the grate, John swears and gets to his feet. Sherlock casts him a curious look. "Pen," John hisses, stalking past them into the kitchen. "Sodding thing won't work."

"It's just a pen, love," Mary laughs, pausing beside the name Matilda Graves before erasing the s. "We've plenty."

"Table," says Sherlock, "left side. No, opposite of where you're standing. Yes, there."

John collects the ballpoint along with a fresh cup of hot water, and slips an old tea bag into his mug, cheeks pinkening from the steam. He leans back against the counter; eyes closed, and takes a long sip. Even at this distance the tension he's holding in his body is palpable. Sherlock envisions sitting John down in his favourite armchair and kneading his taught muscles until the soreness relents, and discovers this is an inordinately pleasurable thought. Warmth washes throughout his torso and he blushes slightly, glancing down when John cracks an eye open and catching him looking. Not good. A torrent of guilt swells in his chest. John is getting married, and Sherlock needs to get this—whatever this is—squared away and put firmly behind him. His infatuation will have to burn itself out. It's improper. More importantly, it's unrequited.

As if sensing his discomfort, John comes over the table where Sherlock is seated and pulls out the chair opposite.

"Sorry about the wait," he says, nodding toward the phone.

"It's fine," Sherlock replies and silently chastises himself for sounding too eager.

John frowns faintly and peers out the nearest window at the street below. There's a definite discontentment in his face, an avid longing to be elsewhere. Sherlock feels it too. He misses the exhilaration of new cases, of hunting down information, of defeating suspects and laughing in the dark and devouring Chinese takeaway after. Wedding preparation has become the priority these days, at least on the outside, leaving little room for the old murder and mayhem they both enjoyed.

"There's a small case," he blurts, pursing his lips when John glances in his direction. "Lestrade mentioned it a few days ago. I could—call him and ask. If you're amenable," he adds, feeling embarrassed.

John's eyebrows go up slightly. He pauses for a moment before answering. "That's…yeah. I'd appreciate that."

"Good, I'll do it after I finish with this."

John settles both elbows on the table and looks at Sherlock. A smile plays at his lips but it doesn't extend to his eyes. Typical pre-wedding John behaviour. Sherlock returns the expression.

"You know you don't have to do all this, Sherlock. It's more than I'll ever be able to thank you for. Mary and I are," John chuckles, pointing his chin toward his fiancé, "quite indebted."

"He's right." Mary nods. "You've been incredible."

Sherlock wants to bask in John's gratitude but that somehow seems immensely inappropriate with Mary sitting just inches away. He tightens his fingers around the phone and ducks his chin.

Mary beams at the forced show of modesty (idiot). "Such a lovely friend."

I am not doing this for you; he wants to snap at her. I am doing this is for John. Only and ever John.

And what a senseless way to demonstrate his feelings, anyway. Helping the object of one's affections get ready to marry someone else doesn't exactly seem like an ideal plan of action, but John has gone and found the person he wants to spend the rest of his life with, and so, in light of this and also in light of Sherlock's feigned suicide and subsequent return and all the trauma that created, the least he can do is assist with the thing that is going to make John happy. Because John Watson deserves, more than anyone else Sherlock knows, has known, and likely ever will know, to be happy. No, more than. He deserves to be elated, blissful, ecstatic. This at the very least.

"I can't wait to hear your composition," Mary adds, and when Sherlock stares at her blankly, prompts, "You know, the one you said you'd play for me and John's first dance."

"Oh!" he says. "Oh, yes. That."

"I'm sure it'll be superb. The only problem is that my future husband here," she grins at John, "absolutely cannot dance."

"Untrue," says Sherlock at precisely the same time as John. They laugh.

John gives Mary a playful poke. "I danced my arse off in Uni, actually. Won an award, in fact."

"Oh, did you?"

"I bloody did."

"Yeah, but waltzing is different."

"You know how; why don't you show me?"

"I don't know how to lead."

"I do," says Sherlock and they turn to look at him, surprised.

"How?" asks John.

"Case. Murderer waltzed with his victims while penetrating them with a needle containing deadly poison."

"Charming."

Mary puts her pen aside, smiling at Sherlock, and, though it could be a trick of the light, a glint of something less benign seems to simmer just beneath it. "Perfect," she declares. "You can teach him."

"I—no, absolutely not. Mary, I can learn on my own, I don't need Sherlock to give me dance lessons—"

"We'll only need an hour," Sherlock corrects, cutting him off. "You'll learn quickly."

"But I'm an idiot, according to you." It's meant to be a light, teasing remark, but Sherlock hates the faint note of hurt that remains behind John's eyes.

He snorts. "Of course you aren't. Do you really think I'd have kept you around for so long if that were true?"

John goes a bit red faced at that, but luckily Mary is absorbed in answering a text message from the wedding photographer. He leans back in his chair and folds his arms over his tartan button down, lips pressed together the way he always does when he is mulling something over, weighing the consequences with annoying care. Sherlock drums his fingers on the tabletop. It isn't good, the excitement he feels at the thought of teaching his ex-flatmate how to waltz, the songs that come to mind: Bach, Vivaldi, Paganini, the sudden vision of John swaying within the encirclement of his arms. He wishes briefly that he hadn't volunteered his expertise in the first place, but where would that get them? He won't have John making a fool of himself at his own wedding. Not that he hasn't wished it on occasion, if he's being completely honest with himself (a spoiled wedding and John back at Baker Street), but again: inappropriate. John's success is, by proxy, his own. And he'd like to keep it that way, no matter how painful.

"Come on, John. Let me teach you."

"No."

"You're being childish."

"I don't want to humiliate myself."

Nor do I, thinks Sherlock, though nervous for a different reason entirely. He places his forearms on the table and sways forward, employing his most amiable expression. "You won't."

John passes a hand through his hair, agitated. "That's questionable."

"I'm an outstanding teacher."

"Oh, are you?"

"Yes." He smirks at John's look of irritation. "I am."

John clasps his hands in his lap, tongue moving along his lower lip in thought. Sherlock does his best to ignore the flash of pink, but not well enough to avoid flushing slightly. He averts his eyes and looks down at the to-do list before him, a punch of adrenaline surging through his chest. This is torture.

"Well?" asks Mary, pocketing her mobile and glancing between them with an expectant smile. "Going to take him up on the offer, John?"

"I—I'll consider it."

"We both know that really means yes," Mary says with a knowing grin in Sherlock's direction. "He just needs a bit of softening." She pushes her chair back and gets to her feet, taking an empty teacup in each hand. "That's where I come in."

She turns and moves toward the kitchen, leaving them in peaceable silence. Sherlock watches her retreating figure, feeling a stab of some indeterminate emotion—a hazy amalgam of envy, sorrow, and resentment. Mary has already insinuated herself into her role as John's wife. She is, apparently, the key to his locked box and she is the one who will persuade and tease and thaw him from now on. To be very honest, it feels as though she's taken Sherlock's job, but he can never tell anyone this. He and John were never like that, so why does it seem as if he's being retired from a beloved vocation, compelled to watch his successor from out in the cold?

"You know I'm going to end up doing it." John's voice, both warm and still a bit annoyed, tugs him from his momentary fog.

"Yes, I'm sure Mary's quite adept at 'softening you,' as it were."

"No." John smiles at last, a real one that reaches all the way up to his delightful eye bags and upturned nose. "I mean yes, she is, but there's also the fact that I never could say no to you. Bastard."

Because Mary is safely ensconced in the kitchen, clattering noisily among the dirty plates and bowls, Sherlock does take a moment to revel in John's compliment this time, feeling immensely warm and fluttery. Stupid, stupid. His scalps prickles beneath John's blue gaze and he moves instinctively forward, near enough to see the varying shades within those corneas in full detail. Thank god he is as good an actor as he is, because sentiment makes it extraordinarily difficult for him to school his features. Thank god John is terrible at discerning truth from fiction.

"So," says John, lifting his arms overhead and groaning at the resultant snapping of his sore joints. The hem of his shirt moves toward his waist. Sherlock leans back, unsettled. "Why don't you hang up and try again later?"

"If I don't do it now it'll mess up the schedu—"

John dismisses this. "I won't have you stuck on hold for hours on end. Hang up."

"Are you—fine." Sherlock punches the off key and lays the telephone aside. He chews his bottom lip. "When do you want to do this?"

"Do what?"

"The dance lesson."

"I've no sodding idea."

"Could do tomorrow night."

"Can't. Mary's going to a friend's open house and I'm coming with her."

"I see." Sherlock rests his chin on his palm. "Tonight, then?"

John considers the offer. "I don't think we've got anything pressing happening tonight, but—" he raises his voice, turning his head toward the kitchen, "—Mary, have we got anything scheduled this evening?"

"Tonight, no. Why?"

John heaves a rather aggrieved sigh. "Sherlock's going to, you know. Teach me to waltz."

"Oh, lovely!" Mary says over the sound of vigorous scrubbing. "I've been meaning to catch up on House of Cards, so I'll stay home with my wine and chocolate and have a bit of me time. By the way, Sherlock, dear, you're running low on dish soap. Just thought I'd warn you so you're not caught unawares."

"All that dish washing you do," John deadpans. "You'd be distraught."

"Shut up," Sherlock snaps, unable to inject the intended amount of vitriol into his tone. It comes out sounding terribly fond and overly permissive. Swallowing a sigh, he glances across the table at John, who's gazing out the window once more, ignorant of his admiring stare. "Come over at seven-thirty and I'll have everything ready."

John gives a snort of laughter. "How much time to prepare do you need?"

Sherlock throws him a look of disdain. "I need to move the furniture, obviously. We can't exactly move freely with armchairs and a sofa in the way, can we?" He immediately regrets the phrase 'move freely' but John seems oblivious. "I may also need to download a few good waltzes we can use to keep time."

"Serious business, this." John draws his eyebrows together in a pantomime of sternness, but his lips twitch at the corners.

"Deadly."

"Right, well, I'll see you tonight then." John flashes him a fleeting grin before rising and striding into the kitchen. "Let Sherlock finish these," he says to Mary, slipping his arms around her waist from behind.

She gives a pleased laugh and pats his cheek. "Alright, love. Ready to go home?"

"Yep." John looks back over his shoulder at Sherlock. A funny softness enters his expression. Sherlock swallows and meets his eyes with a level stare. They regard each other in total silence for several beats. Heat rises in his cheeks. "I'll be back here at about seven-thirty."

"Wonderful. Are you going to eat here or at home?"

John frowns over at Sherlock.

"I'll cook," he says hurriedly and Mary waggles her brows.

"Lucky man," she says to John, giving him a final pat before releasing him and scooping her purse from the floor. "Chemists tend to be very good cooks."

"Yes, well, Sherlock is a bit of an exception to that rule, I've found."

"It's true," says Sherlock, mostly for John's benefit. "I'm hopeless."

"I don't believe it." Mary gives him a quick hug, which he returns somewhat awkwardly. He wonders what it feels like to embrace John. He's never, even after all this time. He decides it must feel very, very good. "I'll see you tomorrow, probably. Ta!"

"Goodbye," says Sherlock, and falters when John brushes past him, that accidental touch burning his arm like a brand. The door swings shut behind them and he lets out a breath he didn't realise he'd been holding. He has five hours until John returns for his lesson. Five hours to silence the swarm of butterflies in his stomach. He turns and heads for the kitchen, setting about finishing the rest of the dishes. He works in a haze, trying not to think about John as he does so, but he can think of nothing else. Wanting to touch John, wanting to invade his personal space, see if he can provoke a level of reciprocation. He imagines drawing John close when they practice tonight, a shiver of pleasure burning along his spine. With each minute that slides past, some new desire suggests itself, some new possibility of the way they could happen. It's with great bitterness that Sherlock remembers the fact that, in actuality, he can have none of them.