The next two days were awkward, but relatively quiet - John and Sherlock weren't avoiding each other, exactly, but neither of them went out of their way to say much. It was only natural, John supposed - whatever-it-was that had happened between them, it was clearly something Sherlock wasn't prepared to process. Odd, to find something his oversized brain couldn't cope with in a matter of seconds.

Thus it was a complete surprise when Sherlock started a conversation one evening with an offhand, "I've been watching a lot of porn."

John choked on his own tongue so badly his eyes watered. "Pardon?"

"Porn, John." Sherlock paced toward him, until they were toe-to-toe and Sherlock was looming over where John was curled on the couch watching the telly. "I've been watching a lot of it since . . . before."

Ah. John's perfectly adequate intelligence made some connections. "Research?"

"Exactly." Sherlock frowned. "I was expecting your browser history to only contain porn with women in it, but you have an impressive variety."

John drew in a deep breath, held it, and exhaled slowly. "You went through my browser history. Sherlock, I delete my browser history, for that very reason."

Sherlock waved John's objections away with a graceful wave of his hand. "Took me less than five minutes of digging. But it was helpful - I didn't know what I was looking for, so I appreciate you having narrowed the field down for me, as it were."

John rubbed his forehead. "Christ."

"So." Sherlock locked his hands behind the small of his back and resumed the pacing he had been doing before he started this incredibly odd conversation. "I'm definitely not straight, but I don't think I'm gay either. Actually, not a lot of what I saw did anything for me, physiologically, but I felt it best to be thorough. And of course, it's possible it was the live element - you being physically here in the room - that made the difference. Before."

"Possibly." John couldn't believe he was actually discussing this with a straight face.

"I wasn't able to test that hypothesis, unfortunately," Sherlock continued. "I attempted to convince Molly to 'talk dirty' to me yesterday, but she actually refused. First time she's refused me anything, actually, and she was altogether acting odd about it."

John's laugh bubbled out at that. Sherlock's eyebrows drew together in confusion, but John couldn't keep a straight face -

"Sorry. Sorry! Just - the thought of you propositioning Molly -" He snorted again, then forced himself into a more sober expression. "Sherlock, you can't just go around demanding people talk dirty to you. Especially someone like Molly, who has fancied you for ages."

"Why not? You didn't seem to mind."

That's the rub, isn't it? John pinched the bridge of his nose and suspected the whole I'm not gay thing might not be the unassailable truth he had always assumed. Trust a mad detective to drag that out of him. "It's not . . . it's not an experiment, Sherlock. Not something you can demand data for."

Sherlock blinked. "Right now I have a sample size of one. That's not data, John, that's an anecdote."

"Christ." John looked back up, forcing himself to look his flatmate in the face. "What did you say to her, anyway? Volunteer to drag her into a janitor's closet for a quick shag?"

Sherlock recoiled at the suggestion. "Molly? No, of course not! I merely requested her assistance with an experiment, which she was quick to promise. And then I said I wanted her to describe having sexual intercourse with me, in as much detail as possible. And she sputtered and looked like she was going to cry and she ran off."

This time John managed to catch the laugh before it escaped his lips. "You're hopeless."

"High-functioning sociopath."

"Doesn't that make your one-person sample data invalid?" John realized what he had just said - or at least failed to contradict - and raced to backtrack. "Not that I think you're a sociopath, Sherlock, just . . . from an experimental standpoint -"

"No, you're right," Sherlock conceded. "I may be a sociopath, but I'm not a robot." He frowned, quick flicks of his eyes taking in John's posture as he sprawled on the sofa, probably his pulse and breathing rate and God knows what else. "I want to have sex with you," he finally announced.

John's train of thought - such as it was - derailed completely. "Sorry, what?"

"I want to have sex with you," Sherlock repeated, a hint of annoyance in his voice. "I want to place my knees on either side of your hips and sit on your lap facing you, and I want to push my tongue into your mouth. I want to cup my left hand around your cervical vertebrae to anchor your head and prevent you from accidentally pulling away, and I want to use my right hand to trace the skin over your cheekbone and your jawline. And I want to grind my pelvis into yours, so I can feel your erection against me as I do it."

"Christ, Sherlock." John knew there was more to it than that - more he should say - but the word erection seemed to have short-circuited something.

And Sherlock had no intention of stopping his monologue, it seemed. "I want to use my tongue and my lips and my teeth to elicit a stronger response from you during the kiss," he continued. "I want to hear you make involuntary noises against my mouth. And I want to trace from your cheek down over your chest, skipping over that frankly hideous jumper, until I can tug the hem out from the waistband of your trousers and slip my palm inside to touch your bare skin. I want to run my hand upward underneath your shirt and your jumper, high enough I can feel the hair on your chest between my fingers. I want to trace mathematical equations across your chest with my fingertips, just to know that you can feel the contact too."

Mathematical equations . . . what -

"And then I want to strip off your jumper, and your shirt, and my own if you haven't done it for me already by that point. I want to have your naked chest pressed against mine, so I can feel your chest hair tickle against my nipples." He smiled a bit, taking in the stunned look John was certain must be showing on his face. "I have particularly sensitive nipples, John. You might want to know that. I didn't realize there was a range, but my research over the last few days confirms it."

"Ah . . . good to know . . ."

"Yes." Sherlock bit his lip. It was probably a practiced move, but fuck it was having the intended effect on John's libido. John felt like he had been poleaxed by something entirely unexpected and - until now - invisible.

"I want to find where your nipples fall on the range of sensitivity, too," Sherlock added. "Are you within a standard deviation of the mean?"

"I -"

"I'll make sure to excite you, too." Sherlock tilted his head back, tracing one long finger slowly down the pale column of his throat, and John's mouth went dry. "You want to suck hard enough to leave a bruise on my neck? I'll tilt my head back like this so you have all the access you require. Break as many subcutaneous blood vessels as you like - leave a ring of bruises around my neck like a collar, like a pre-coital 'John was here' sign. I'll wear them proudly. Lestrade won't say anything, of course, but Donovan and Anderson surely will. They'll congratulate you."

John swallowed. Hard. "Sherlock, I wouldn't -"

Sherlock pressed on, talking over John's stumbling objections. "I want your mouth on me, John. I want your mouth over my carotid and my pectorals and my nipples and my abdominal muscles and my testicles and my penis. Particularly that last one. I want you to use your mouth to turn my brain off completely, to redirect blood flow entirely to my groin. You're proud of how good you are at fellacio? I'm metaphorically aflame with anticipation to learn just how accurate your assessment of your skills is. I want you to make me moan, John, to make my vision flicker and the muscles in my legs temporarily weaken as you conduct your own experiments on me."

"I've never been with a man!" John cried. Bloody hell, did I just say that out loud? He forced himself to take a deep breath. "Sherlock, those things I said the other day - I mean, I've dated plenty of women, but I've never given a blow job before. I was just trying to . . . to rev you up a bit. I've never . . . fuck."

"I know." Sherlock smiled that insanely patronizing smile of his. "But you want to. I was watching closely before - you were just as affected as I was. You're aroused at the thought of performing fellacio on me. Of putting your fingers through my anal sphincter and trying to stroke my prostate. And I'm very, very interested in it as well. I think I might like to try the reverse, too - I'm curious what your pre-ejaculate tastes like, and whether the skin on your neck tastes different from the skin over your stomach or the skin on your penis or the skin on your testicles. I think the next time you take a shower, I'm going to go lie on my bed and cup my own genitalia in my hands and think about what you look like when you're wet and naked." His fingers curled at his sides, as if he was trying to force himself to keep them there. "I'll leave my door open, so when you get out, you can see me lying there, my skin flushed from arousal and exertion and my eyes closed so I won't know until you come into my room whether you've decided to come touch me or not."

John was very hard now. Frustratingly, achingly, hard, despite how Sherlock kept using the word "penis." And Sherlock was looking at him, waiting patiently for John to do something, but John didn't want to get up as long as he had that raging erection - surely Sherlock would see -

"It's all right, John," Sherlock said quietly. "I've gathered as much data as I need from you for the time being. You don't need to hide that you're aroused."

John groaned and levered himself off the couch. "I think I need a cold shower."

He realized the implications of his announcement - so close on the heels of Sherlock's - a moment too late. And there was no hiding the wave of lust that slammed through him at the sight of Sherlock's face in that moment.

"I'll leave the temperature up to you," Sherlock said softly. "But I'll be waiting in my room."