After that incident, despite the handy excuse of being very deeply in shock for most of it, Sherlock is unable to pretend that the way he thinks and feels about John is mere lust or fascination or even strong affection for a trusty comrade. The problem is, he has no frame of reference for exactly what it is that he's feeling.

Sherlock has begun to stare intently at John whenever he thinks John isn't looking at him. The man seems to have developed a permanent glowing aura around him, sometimes brighter, sometimes dimmer, but Sherlock can see it even when he closes his eyes. It hasn't gone away since that day. It's not that it was never there before, but more like Sherlock hadn't been able to see it until then. Because now it seems such a vital part of John's persona that Sherlock can't imagine him without it.

He carefully asks Mrs. Hudson one day if she's noticed a sort of halo around John.

"Only after I've had my evening soother," she tells him, giving him a concerned look and a pat on the arm.

Was he always burning this bright, must have done, he's still the same John as he ever was, but how can someone stand to be that lit up all the time, how does he sleep, is it ever dark behind his eyes like it is behind Sherlock's…

It slowly dawns on Sherlock that for the first time he is experiencing what it is to want someone. And that he has been for some time, he just didn't know what it was before. It's…unsettling to say the least. Not that he's never wanted before, that would be ridiculous. But that was the wanting of an act or a sensation or of simple relief; the person involved was largely irrelevant. But now the person is the point of it all, and the other wants are only expressions of the need for that person. He's never encountered anything like it.

At uni, Seb had always been good for a reliable fuck, despite his annoying insistence that it wasn't bent so long as they didn't have a "proper" shag, and the hatred between them served as a spark which, if not akin to love, at least did a passable nod to passion.

It was less complicated than the deeply closeted underclassmen who sometimes sought him out and tended towards the clingy and unstable. At least he and Seb had known where they stood and exactly what they wanted out of the whole thing. But eventually Seb's bullying and proclamations of his essential heterosexuality began to wear thin, and Sherlock had found his interest in hurried encounters and being sucked off behind the gymnasium late at night waning.

Of course he'd done his own share of that during his junkie days, sometimes from sheer need for gratification, sometimes in exchange for drugs, but there'd been nothing more serious than that and precious little at all since, even including the odd experiment. Not once in all that time had he found himself openly, hopelessly desirous of another human being for their own sake.

It isn't that he wants to fuck John.

Oh, God, how he wants to fuck John, he wants to crawl inside of him and try him on like a new suit of clothes that's been tailored just for him and calculate mathematically every possible way their bodies could physically fit together and then try them out in order and rate them by mutual satisfaction level…

It's that he wants John, for his very own, in every possible way one human being can want another.

To possess, to inhabit, to wear on a chain around his neck and press between the pages of a book and keep safe forever where only Sherlock can look at him and no one else can ever have or touch him and he'll always stay perfect and beautiful and good like he is now...

He wants that magnificent incandescence that is flowing out of every pore of John's skin within himself, to push back the blackness that is constantly threatening to overtake him. Sherlock is made of darkness and shadows and deep blue ice, but John is made of supernovae and magma and dry desert winds.

When hot wind meets cold ice, what happens, will he end up as a puddle, destroyed, melted away forever, nothing left or will he just be saved from freezing over entirely and becoming unreachable like he nearly was before, trapped in the frigid supercomputer of his own mind…

These new thoughts startle Sherlock, as if they come from someone else and are inserting themselves fully formed into his brain. He is aware that some of them might even be Not Good, but they are so intense and alluring and completely irresistible that he can't bring himself to care. He is fascinated by these ideas, turning them over in his head, playing with them like shiny toys and watching how they reflect the light.

He knows these are not the kind of thoughts you can simply keep in your head and look at once in awhile and never act on. These are the kind of thoughts that draw you in, that get stronger and more urgent the more you entertain them and that, eventually, demand action. The problem is, Sherlock has absolutely no idea what to do about them.

In the end, however, it's not left up to him. One afternoon, a few weeks after the gristly conclusion of the abattoir case, Sherlock is, if he's honest with himself, daydreaming on the sofa, sprawled out on his back, when he realises John is standing before him, talking to him and looking serious.

"Pardon?" Sherlock says, trying to disperse his thoughts enough to focus on his friend.

John exsanguinating Sherlock's attempted killer with a look of rage so terrible and justified that Sherlock had thought looking into it might burn his face off and he would have been fine with that, really, so long as it was the last thing he ever saw…

John looks annoyed. "I said, ever since you got out of hospital, you've been staring at me like you're about to make a meal out of me. Should I be concerned for my safety, or do you just have too much time on your hands?"

Sherlock freezes. He thought he'd been more subtle than that. He swallows. "I don't know what you're talking about, John."

"I'm sure you don't," John replies, dryly. He decides to try another tack. "I've been thinking…since the abattoir… maybe there are some things we need to…sort."

Sherlock arches an eyebrow, remembering the overheard conversation with Lestrade that now is starting to make sense to him.

He does go half mad when John's in danger, but John wasn't meant to know that, nor about any of the million other things they might need to get sorted, so how does Lestrade know about them, that git…

"Do you…maybe feel like that's true?" John hazards.

Sherlock nods warily, wondering if this is a trap.

"Christ, Sherlock, don't make this difficult for me! You're the one who's been undressing me with your eyes every time I turn around for the past month." John's turned a funny shade of pink and Sherlock can't tell if he's embarrassed or angry.

"I'm…sorry?" Sherlock offers, lost.

John makes a sound of complete frustration. "Fine, you're a tactile learner, we'll just have to do this another way..." Then he does literally the last thing Sherlock expects. He flops gently down on the sofa on his stomach, square on top of Sherlock, so that John's head is just at the level Sherlock's collarbone. John rests his chin lightly on Sherlock's sternum and looks up at him. "Worked it out yet, genius?"

Sherlock stiffens. "I…um…"

"How about this: good or not good?" John, so confident a moment ago is starting to look uncertain.

"Good," Sherlock says hurriedly. "I think…good."

John's body pressed against his, so casually intimate, so warm against his chest, starting to shine brighter now, the whole room is aglow, what must it look like from through the window, and he does want to make a meal out of John, many meals, and to undress him with more than just his gaze…

John smiles at that, all crinkles and stardust around his eyes, and pushes himself up on his elbows so their faces are just a few inches apart. Slowly, giving Sherlock plenty of time to object, he puts his lips to his friend's and presses them together, slipping his tongue into Sherlock's suddenly open mouth and gently caressing Sherlock's own with it, tasting him, sliding over him as softly as warm waves lapping the shore of some tropical sea.

Sherlock wonders briefly if this is what it feels like when the sun explodes in your mouth, too stricken even to respond properly, just losing himself in the flavour of their mingling saliva and the feel of John's slightly chapped lips on his.

And his smell, like wood smoke and wool and the second pot of tea when he's reused the leaves and gunpowder and blood pumping through his veins so close that Sherlock can feel the coppery taste of it pulsing in his own mouth…

John pulls away gently, too soon but not before he's left Sherlock's brain in the state of a Sunday pudding. "Good or not good?"

"Oh." Sherlock breathes, stunned. "I…good."

John smiles at his reaction. "Are you okay?"

"Kissing isn't really…wasn't really ever much of a part of my… activities… not that kind of kissing, anyway. That was…very different than anything I've done before."

Hard and angry and perfunctory and horny and dominating and shameful kisses all featured more or less but never sweet or tender or slow or sensuous or promising or caring or warm and certainly not all those things at once…

John cocks his head, and makes a move to get up. Sherlock follows his lead and they sit cross-legged on the couch, facing each other.

"Sherlock, I know this is kind of an awkward question, but considering…" John clears his throat. "Are you… I mean, you have…um… you're not a…?" He's a gratifying shade of bright red now.

"That depends on your definition," Sherlock replies primly, resorting to clinical terms to hide his embarrassment. "Various kinds of sexual contact, yes, but nothing penetrative or that would be termed intercourse, with either gender."

No proper shagging, that was too personal, too close to meaning something, too dangerous, and maybe he'd resented it at first but now he's glad he doesn't have that memory with Seb or some junkie whose name he didn't know to haunt him, when none of it had mattered anyway…

John looks like Sherlock just hit him over the head with the Cluedo board, but holds it together admirably. "Oh. Well. Thank you for telling me. Me neither. Er. I mean, yes, with women, of course, obviously, but not…um. Yeah. Well. We can learn…with each other. I mean, um, if you want to."

Sherlock's eyes widen. If he wants to.

He wants to do nothing but lose himself inside of John, to have John fill him up with his blazing radiance and burn away all the darkness inside of him until he is reduced to a little pile of ash that John can sweep up and keep in his pocket or scatter in the winds as he chooses...

John misinterprets his expression. "Oh, God, Sherlock, I'm sorry, I didn't mean, we don't have to… I mean, I just thought we should talk about it…"

Sherlock shakes his head, going very still, overwhelmed, unable to find the right words to make John understand, and John is getting upset and he's going to go away now.

He'll be gone and there will never be another chance and the light will dim and Sherlock will never know what it's like to live at the centre of a supernova or be wrapped up in fairy lights or own a tame thunderstorm…

John is getting up to leave, he's hurt and humiliated and Sherlock still can't move and he's going to walk out that door and never come back.

Somehow, Sherlock manages to shoot out one hand and grab John's wrist like an iron manacle. "Wait," he gasps, as if he's been held underwater without oxygen for too long. "Please, John. I just… it's all a bit much."

John takes a deep breath and sits back down, slowly. "Can you tell me?"

Sherlock doesn't trust himself to speak or move again yet, but gives an almost imperceptible nod.

"Okay. Take your time. When you're ready."

Sherlock is motionless and silent for a long time, collecting his thoughts, then they all come out very quickly, in much more of a tumble than he intends, things he's had running through his head but never thought would come out of his mouth.

"I don't know what I'm like, John. With someone. Back at uni it was all hurried wanking and sucking each other off and pretending no one knew and it didn't mean a thing, and since then it's been my work. I think I might be horrible at it. I think I might be terrifying, if I let myself go to that place with you."

John's expression softens. "What do you mean?"

Sherlock shudders involuntarily. "I'll want you forever, and I'll never want anyone else to have you or look at you or touch you, ever, as long as you are alive. I'll be jealous and possessive and petty and unreasonable, and I think I would hurt you rather a lot, and often, and not care about it as much as I should. I'll take everything you can give me and still demand more, even if it's too much. I wouldn't let you go even if you wanted to and if you tried to leave I would hunt you down and lock you up so you could never do that again. I'll take you apart piece by piece just to see what makes you tick, turn you inside out to see what you're made out of, and maybe never put you back together again. I'll be callous and cruel and dangerous and I think I might end up destroying you…"

John is silent for a moment, taking all that in. At last he says calmly, "So…just like now, then, but with sex."

Now it's Sherlock's turn to be hurt, but John grabs his hand and laughs gently at him and somehow that makes it better. "Sherlock, I know you already, remember? I live with you. You don't think I would have tried to start anything if I hadn't already thought about all this? You'll be a fucking nightmare and I'll love every minute of it. It's what we do."

Before Sherlock can respond, John leans forward and starts kissing him again, and Sherlock's brain goes blissfully bright for awhile, like the sun on a snowfield at the solstice, until somehow they are back with John laying facedown on top of Sherlock, draped comfortably across his torso, using Sherlock's breastbone as a pillow while he plays idly with his curls.

And it has to be a dream, it has to be, because that is the only way he could possibly be laying on the sofa with that sandy blonde head resting on his dove grey shirt and steady hands trailing against his scalp and the taste of his best friend still in his mouth…

Sherlock doesn't want to move or speak, but he feels he should make one last effort to warn John about what he's getting into. "I don't believe in love, you know. And I don't have a heart. I think that might be a problem. "

Love is just chemicals, he can name them one by one, diagram them on a chalkboard, detail what causes them and what physical effect they have on the human body and how to trigger them and how imitate them and how to get rid of them so whatever it is he's feeling now can't be love because love is just a magic trick and this is so very real…

John gives him a patient look and puts his ear to Sherlock's chest. "Nope, you do. I can hear it and everything."

"No, I have a four chambered muscle that pumps blood and oxygen through my circulatory system. You've got the heart, a great big one, and it's hot like the sun and glows like an aquarium of fireflies."

John smiles fondly at his unexpected poetry, although Sherlock doesn't think it's poetry, it's just the only way he can think of to explain it. John cranes his neck and kisses Sherlock in the tender spot right where his jaw meets his throat, the pulse point. "Well, then I probably have enough heart for both of us."

Sherlock feels reassured by that, even though he knows it doesn't really make sense. He tentatively puts one arm on John's back and is surprised when John kind of curves his body up into it, making a low noise of contentment that he's never heard before.

"What happens now?" he asks John.

"What do you want to happen?"

He wants to rip off John's clothes and bend him over the coffee table and die inside of him and he wants John to hold him down and ravish his body until he's screaming for release and he wants them to stay exactly like this for years and years with the brightness of a thousand suns curled up on his chest in a questionable cardigan, like a fire opal wrapped up in brown paper and only he knows what's really inside…

"Everything," he says at last, and John somehow understands completely.