Disclaimer: This fan fiction is not written for profit and no infringement of copyright is intended. Not beta read so all mistakes are mine. Thanks for their reviews go to kraftykathy, Poodle warriors, Emma Lynch, lavanyalabelle, Equal-Opportunity-Reader and Katya Jade. Be aware, there's more D/s shenanigans in this one and some (naked) character development. You have been warned...

- EXCHANGE -

The first thing that Molly tells him is that he's going into rehab.

She does not present this to him as a choice, simply as a prerequisite for their doing anything more together.

Sherlock knows that he should be angry with her for ordering him- He's been ordered into rehab by just about everyone he loves at some point in his life, it's the Holmes' family version of golf- but when Molly says it, somehow, he doesn't mind it.

After all, when he wanted an excuse to break his sobriety, he found a case which allowed him to do it.

(He may not want to admit that to John or Mycroft, but he knows it's the truth).

And now, now that he wants an excuse to save himself, broken, twisted, blackened thing that he is, now Molly is providing that excuse.

(Maybe he knew that she would, maybe it's one of the reasons he wants her so badly).

And maybe if she wants to save him then he's actually worth being saved.

So he agrees. She says she will do the things he asks so long as he is clean when he asks them; She refuses to engage in any activity with him if his consent is in any way dubious and furthermore, she informs him that if he breaks his sobriety again she will, "kick his skinny arse to the curb."

Resistance is therefore not so much futile as idiotic.

Sherlock suspects that he would be able to talk her around, even if he did have a lapse- his Molly loves him, he knows that. But though he may feel reassured in his belief that he can never lose her, the thought of her, worrying and pining and hating herself for giving in despite the fact that he's broken their agreement, that sets something gnawing at Sherlock which in another man might almost be called… conscience.

Conscience, he thinks. Where the bloody hell did that come from?

Rather than examine any unwanted (and hither-fore unsuspected) emotional growth however, he merely promises himself and her that he will stay clean. He will. He's done it before, he can do it again. It's what she wants from him. It's what he's promised to give her.

And if he does that then she says that she will restrain him. Hurt him. Make his fantasies reality, take over from him when it all becomes too much. She'll keep him safe, she promised.

And maybe she'll even find some way to keep him safe from himself.

So he does as she asks, goes through with his side of their bargain. The very thought of it makes Sherlock's bones vibrate with longing, the image of Molly's lovely mouth giving him her consent enough to get him through thirty dreary days of group therapy and visits from Mycroft and the Watsons and all sorts of texts and phone-calls from Lestrade and his people in the Yard.

It's not like he really needs to be here, he tells himself sometimes. It's not like he actually was an addict again.

It's not like he'll give into his appetite for drugs now that he has his Molly.

Whenever he thinks that he finds himself remembering John's sad, overly-cheerful expression from his visits. Remembers Mary's hawk-like gaze. Neither seem to believe what he's telling them but Sherlock doesn't care, at least that's what he tells himself.

He must do a reasonable impression of a cured addict though because they tell him he's free to go at the end of his thirty days, and the only person who's actually surprised by this is Sherlock. Surprised, and, little as he is willing to admit it, a mite disappointed.

He won't dwell on that though, not when he's getting out of here.

So he smiles and does his best to act naturally when John and Mary turn up to give him a lift to Baker Street. (He's already texted Molly to tell her that's where he's being brought. She says, and this is the exciting bit, that she'll be over tonight. She's been doing some research.)

Mycroft has sent a town-car but Sherlock cheerfully refuses it, telling Anthea exactly where his brother can stick his offer. Anthea, by virtue of having been around the Holmes' Brothers for years, elects not to communicate this message directly and instead merely wishes him luck, waving to John and Mary before heading out to convey the spirit (rather than the letter) of the message to her boss.

"That went well," John says as she pulls out, though for some reason Mary is watching the government car go with something of a bitter eye.

"It did," Sherlock says, determined not to get involved in another domestic. (It looks almost as if Mary is somehow… irritated with Anthea. How odd). "Anyhow," he says in his best cheerful voice, "how about you get me home? Haven't slept in my bed in a month, you know. It's been all doing my own cleaning and not taking opiates and baring my soul. Very dull."

"We know," John says. He looks at his friend in the car's rear-view mirror, the tips of his ears turning pink. "Well done, mate," he tells Sherlock earnestly after a moment. "I know that wasn't easy, but fair dues to you. I knew you had it in you."

Sherlock smiles and preens- there are few things he likes better than John Watson being pleased with him- but when his eyes catch Mary's she says nothing.

She doesn't look suspicious or anything, she merely doesn't congratulate him.

He remembers her words that night on the swings, about addictions and people like us, and try as he might he can't keep himself from feeling a tiny hint of worry.

This lasts as long as it takes him to get back to Baker Street and for Mrs. Hudson to start to fuss and then it deserts him. He finds all his laundry done and his tea waiting, and just for a moment it's like he never left. After John and Mary leave Mrs. Hudson tells him she's heading out for an evening with a "friend," (Mr. Gupta. Widower. No wife in Doncaster- or anywhere else- this time. Minor marijuana habit, but that can be overlooked. Sherlock approves.)

She tells him to call if he needs anything, but Sherlock waves her off. Takes up his violin and starts playing a tune that's been going around in his head for a month.

He doesn't want to tell her but he thinks it may be Molly's; He so rarely wants to compose and yet this tune has been running through his mind like a good memory, over and over again.

Molly is the only entirely good memory he has right now, so he thinks that it must be down to her.

Mycroft texts him but he ignores it, only answering when it occurs to him that his brother may actually send operatives to check on him. The elder Holmes seems pleased (well, as pleased as he ever is) with Sherlock's recovery and for this reason his answering text is almost… chipper. Bordering on upbeat. Sherlock would engage in their usual tête-à-tête (or as John terms it, Their Satanic Majesties' Pissing Contest) but he's waiting to hear from Molly so that takes up a great deal more of his attention.

An hour passes, then two, and still he hears nothing.

Worry starts to set in.

He's just about to put on his coat and go over to hers when he hears the doorbell ring. He can tell by the length of the press that it's not a client- He thunders down the stairs, pulls open the door and prepares to greet her with just about anything she asks for.

Instead though, he finds her standing in her tatty old coat, a taxi at the curb.

"We're not doing this here," she tells him by way of greeting. Her expression is… guarded. Cold. Something in Sherlock shrinks slightly, at the sight of it.

"Don't you want to come in?" he asks.

She shakes her head, her arms tightening on herself against the evening's chill. "Go upstairs, get your coat and wallet," she says instead. "You're paying for the taxi.

Bring anything you need for the morning."

Sherlock looks at her face, sees the coldness in it. The distance. For some reason he doesn't want to examine, Irene Adler and that awful night in Karachi pop into his head. The Woman had looked at him like that when he offered her his company and his body.

It's why he hadn't been able to go through with it in the end.

But that look had been natural on Adler, part of who she was. Part of what she was. It was the look which had finally convinced him that he could stop torturing himself, that he wasn't in love with Irene bloody Adler, that he hadn't made a mistake in letting her go.

Seeing it on Molly's face is… wrong. She shouldn't look like that, she just shouldn't.

Not knowing what to do however- he asked this of her, he told her it was what he wanted- Sherlock does as he's told. Fetches his coat and his wallet.

His violin lies, forgotten, on the sofa because suddenly there's no Molly-Tune in his head.

She doesn't speak in the car, doesn't touch him. She certainly doesn't kiss him and that- Sherlock realises that he had been looking forward to that more than almost anything else. Molly didn't kiss with half her attention, she throws herself into it. There's no halfway with her, you just get dragged along in her wake, basking in how good it feels. Sherlock knows that he has little experience and he suspects that she has more but it has never worried him, because you can't be worried when you're being kissed by Molly Hooper, it's a physical impossibility. And yet-

She gestures imperiously and he pays the cabbie. He trails up her building's steps after her, silent as she unlocks her flat and lets him inside. She goes to the small two-seater sofa in her living room and when he moves to join her she holds her hand out. Halts him.

He blinks at her in surprise.

"From here on in," she says. "You ask permission for everything, and you do as you're told, is that clear, Mr. Holmes?"

He can hear the arousal in her voice when she refers to him like that, and it makes him feel some modicum better.

"I said, is that clear Mr. Holmes?" she repeats and he nods. Clears his throat.

"Yes," he says.

"Yes, what?"

He thinks of what he called her the night she told him he was going into rehab. "Yes, my Molly," he says quietly.

He sees something, some flash of emotion move through her face as he says that. For a split second she is flustered. For a split second she is his Molly again.

But then the cold mask is back and she cocks a cynical eyebrow.

"There are a great many other words for a woman who does what you're asking me to do," she says. "Pick one, or I'll choose for you."

Sherlock feels a tug of hurt at her words. Where is the Molly who accepted his gift and kissed him and stroked his hair last time? He wonders. She was happy to be his Molly.

Maybe that Molly was an illusion. Maybe that Molly only exists in his head.

He looks at the woman before him, sees her stare back, almost daring him to say anything- And then suddenly she breaks eye-contact. Her fair skin flushes scarlet and she doesn't want to look at him.

For the first time tonight, he thinks they might be on the same page, and that page is the dictionary definition of confused.

"I'm sorry," she says then. "I know you want a proper domina, but- I don't think I can do this, Sherlock." She looks up at him, the brown eyes plaintive. "I can't- I can't talk to you as if I don't care about you," she says. "I could never do that-"

"What on Earth makes you think you have to?"

Sherlock doesn't mean to say the words quite so loud, but really. He would have thought Molly too clever to buy into all those myths about BDSM, myths which even he, the so-called "Virgin," had known to take with a pinch of salt.

She blinks at him though, her expression almost hurt and inwardly he winces. Maybe he should have talked to her more that day when he gave her the fan: He told her everything he wanted for himself, but he didn't explain what he wanted from her.

Maybe that's how she got the idea that he would want her to behave like some sort of evil version of herself, or perhaps some sort of femme fatale, like Adler-

It clicks then. Of course, she would be the logical place to start Molly's research. His pathologist is nothing, if not thorough. And thanks to John's blog, The Woman is his best known weakness.

It occurs to Sherlock that if Irene Adler could see the trouble she's causing he and Molly right now, she might well laugh her arse off.

"You looked up The Woman, didn't you?" he says, and Molly's silent, mortified nod is more than enough to tell him he's correct.

For once, he really wishes he wasn't.

"It seemed like the place to start," she says quietly. "You- You liked her so much, you were so fascinated with her-"

"And I left her in Karachi without even being able to bring myself to undress for her," he says, speaking over her.

He supposes he should be embarrassed about that last detail but really, if Molly's upset he has more important things to be getting on with.

At Molly's surprised blink he sighs. Rakes his hands through his hair. He has a feeling explaining this is going to be mortifying. "I tried," he says quietly, "Did I not say as much? And the person I tried with was Irene Adler. But she couldn't- I mean, I couldn't-"

Molly stands. Closes the space between them.

Suddenly, she's merely an arms' length away.

"She couldn't take care of you?" she asks, and there's something odd in her voice, something sweet and kind and longing and, and hopeful, that just stops Sherlock in his tracks. Makes him stare at her.

She blushes under his scrutiny, and oh but it's a long time since she's done that. He hadn't realised he missed it.

He nods. "Yes," he says, very quietly. "She couldn't…" He makes himself say the words. "She couldn't take care of me. I couldn't- I couldn't have ever turned my back on her, even for a moment. She's not at all like you."

And he reaches out, very hesitantly, and places his palm upon Molly's cheek. The fall of her hair whispers against his fingers. Molly closes her eyes at his touch, leans into it. Her own hand steals up to come to rest directly on his heart and without his bidding it to, his free hand comes up to cover it.

They stay like that for a moment, simply breathing together and then Molly opens her eyes. This time they're warm. Open.

They rest on Sherlock with a palpable weight.

"Undress for me," she says, very quietly, and it's different this time. The tone of voice, it sends a shiver right up Sherlock's spine. He feels lost in it. He can feel his blood start to slow, to thicken. It pools, languid as lava, in his veins.

She stares up at him with heavy-lidded eyes and he feels like they are the only two people left in the world.

"How do you want me to undress, my Molly?" he asks, and this time when he says it she smiles at him. The hand on his chest trails down, lightly, slowly, to trace his abdominals, his belly. The sensitive flesh below it.

For a moment he thinks she'll trace the line of his crotch but instead her hand slides around. Moves to tease his right arse-cheek. It fills her palm, she squeezes, and really, he's surprised by how good it feels.

His hips jerk a little in response, his cock hardening, and that feels good too.

"Slowly," she says, whispering the words, singsong, into his ear. "Take your time. Let me see you."

Sherlock cocks a cynical eyebrow. "You don't expect me to dance or something, do you?"

She snorts with laughter and despite himself, Sherlock smiles too. "No, your nudity will be sufficiently entertaining," she says. "Unless dancing is one of your kinks as well?"

An image pops into his head, he and Molly naked, her standing on his feet and her head rested on his chest as they sway. It looks awfully peaceful.

But that's for another day, a day far in the future, and so he shakes his head. Reaches down and shyly rests his forehead against hers. "Nope," he says, popping his Ps. "But I'll let you… I'll let you see as much of me as I can."

Suddenly Molly's taken his face in her hands, tilted it down towards her. "Show me as much as you're willing," she says quietly. "As much as you're able. Nothing more."

She kisses him and if he'd had any doubts, ever, about how Karachi turned out they'd be dismissed right there.

She steps away from him and returns to the sofa. Their eyes meet, lock, as his hands move up to loosen his tie. It's actually quite distracting, trying to remember how to open the knot with those big brown eyes staring at him, but eventually he manages it. Pulls the tie loose and over his head, places it over the back of the kitchen chair to his right.

The buttons of his shirt are similarly difficult, finicky, but he manages to get them open. He places his cufflinks beside his tie as he slides the shirt off, as he tries to fight back the flash of annoyance, of vulnerability, which he feels as he stands before Molly without so much of the armour he normally wears.

She however merely stares, her eyes widening in appreciation. Sherlock had always known that women found him attractive, but this feels different. Molly knows the worst of him and she can still stare at him like that. As he thinks this he moves onto his trousers, reaching down and opening his belt, trying not to notice the way Molly's tongue darts out to lick her lips as he pulls the leather loose-

He's about to set it beside his tie and cufflinks but she holds her hands out.

Without hesitation, he places it onto her flattened palms, inclining his head slightly as he does so. Trying not to swallow too hard as she runs her hand delicately up its length.

Those small hands have a fierce grip, he thinks.

"You may proceed," she says quietly, and he has no idea why but Sherlock can feel the blood rush to his face, the redness swarming underneath his skin even as his cock swells to a greater hardness-

"You're nearly there," she says quietly. "Show me the rest. Please."

For a moment her hand twitches, as if she means to reach out and touch him again, but at the last moment she pulls back. Her knuckles tighten around his belt.

Sherlock swallows, undoes the buttons of his trousers and pulls them and his underwear down at the same time. He wonders whether she will object at the shortcut but she says nothing. Again her eyes are widened in appreciation of the show. He kneels down and opens his shoe-laces, toes off both socks and shoes and when he stands up he is absolutely naked.

He normally has no problem with nudity.

He's not feeling terribly normal at present.

He looks at his feet- Where the Hell else is he going to look?- and as he does so he sees the toes of Molly's shoes enter his field of vision.

When he glances up she's standing close to him, the belt held in her hands.

"I originally wanted to tie you up with this," she says, very quietly, and her eyes are fastened, as his are, on his shoes. "I thought of you like that, held in place for me by something which was still warmed by your body heat. It… It made me feel wicked." Her eyes flash up to him suddenly. "Do you think that's wicked, Sherlock?"

He nods. "Yes, my Molly."

She swallows, looking a little nervous. "Good," she says. "I was thinking that you'd like that. I know I would." She shakes her head with mock-mournfulness.

"Unfortunately however, I'm afraid I can't do it," she says. "The leather, it might dig into your wrists. Might mar this beautiful, beautiful skin. Chafing would be noticed- so many questions at Scotland Yard- and I know I don't want to injure you…"

Her fingers reach out, trail against his wrist, up his arm. For some reason he can't imagine, it feels quite familiar.

She's watching him very carefully as she does it, those eyes dark and wide.

Sherlock swallows. "So what will you do to me?" he asks, and this time it's his voice that's thick, his tongue that feels heavy.

Molly's looking at him awfully closely, her expression intent. There's a knowing sort of wildness in her now

"Why, I suppose I'll have to tie you up with something else and use the belt on you," she says matter-of-factly. Sherlock's cock practically leaps at her words; he feels, for a moment, almost like a trained hound. "Would you like me to use this belt on you?" she asks quietly. "You have to say the words, Sherlock."

He takes a deep breath, tries to steady himself. "My Molly, will you please use my belt on me?"

She nods.

"Yes. Now take your hands and place them on the wall."

She nods to the one behind her, right beside her bedroom door. He goes to the precise spot she indicated, places his palms flat against the panelling, right beside the doorjamb. She taps his knees so that his legs are farther apart and he feels another shiver go down his spine. It feels oddly freeing, to be so open.

"You will not move," she says softly. "You will not flinch. If you do, I will stop. Is that entirely understood, Mr. Holmes?"

He nods. He can't… He's having trouble speaking right now.

No, he's having trouble thinking right now.

Molly leans in close to him, her skin, her hair, almost touching him, and whispers, "pick a number between one and ten."

He doesn't hesitate. He knows what she's asking.

"Ten," he says, his throat tightening with the effort. "Ten. Please."

It's not a lot to start on, but he needs her to see what he can take.

Ten lashes slash into his flesh.

Ten lashes show him precisely how much his Molly wants to please him.

When she's given them she turns him around, presses him back against the cooling wood of the door as she kisses him. Her fingers soothe the soreness from his flesh as she holds him tight. As she coos at him how well he did, how beautiful he looked spread out for her.

She really is very beautiful, he thinks, with a weapon in her hand.

She takes him to bed with her, and she never removes a stitch of her clothing. Sherlock sleeps good and well that night, knowing that this was a beginning.

A small one.

A good one.

He wakes up the next day next to Molly Hooper and he can't help the way he smiles at her, though he knows she's still asleep.

The belt lies, forgotten, on the floor beside them as the sun creeps in through her blinds.