John's ears were still ringing when they got back to the flat. Apparently it wasn't just a turn of phrase - the nine sailors he and Sherlock had run to ground and gotten arrested that afternoon really had sworn with impressive fluency. And volume.

"Some of those combinations were new to me," he commented out loud. "Rather impressive, really - even though I was in the army and all."

Sherlock shrugged off his coat and made a disapproving sound. "Profanity is a refuge for those with lesser vocabularies. I prefer to be more precise."

"Precision and profanity aren't mutually exclusive, you know," John retorted, more out of a desire to contradict Sherlock than any particular need to argue his point. "Every term has its use." He let himself stare off into the space over the mantel, trying to remember a particular blonde he dated for a while during his years at uni. What was her name? Charlene? No, Cheryl. She had been particularly fond of precision in that aspect of her vocabulary - loquacious, even . . .

"Rubbish." Sherlock collapsed into the couch and propped his feet up on the armrest. "You're talking about during sex, I assume?"

John snorted. "Yes, Sherlock, sex. It happens when two people who love each other very much decide to make a baby - actually, did you ever get the 'where babies come from' speech? I bet it was from Mycroft."

Sherlock audibly rolled his eyes. "Don't change the subject, John. I was just saying, I don't see any way talking dirty - using profanity - could possibly be considered sexy. It's just biology, after all."

"Have you ever actually had sex, Sherlock?"

"Why would I?" Sherlock steepled his fingertips and stared at the ceiling. "It's a biological drive of the body, John, not a pursuit of the mind. Boring."

John couldn't suppress his laugh. Sherlock turned his head and glared, clearly offended at John's response, but really, what else did he expect? "I'm continually amazed," John admitted, "at how phenomenally knowledgeable you are about some things and how mind-bogglingly ignorant you are about others. The mind is the greatest sex organ there is, and sometimes dirty talk is the difference between good sex and great sex. The same physical stimulation but a different biological response, all based on brain chemistry."

"Rubbish," Sherlock repeated.

"Look, just because you've never had good sex -"

"Prove it," Sherlock snapped.

John blinked at him. "Prove you've never had sex?"

"No, John, prove that precise profanity has a purpose. Convince me."

"You want me to talk dirty to you."

Sherlock popped up from the couch and started pacing the floor. "Yes, if that's what it takes. I refuse to believe that mere words could have any effect on sexual arousal. Perhaps in certain situations, clinical terms are useful for negotiating further liaisons, but in neurochemical terms -"

"Fine." John watched Sherlock pace for a moment and formulated his plan of attack. This would be worth it, if only to put the damn detective in his place . . . John stalked toward Sherlock, cutting off his pacing and forcing him back toward the doorway.

"John?" There was a tiny hesitation in Sherlock's voice, and John's resolve firmed. It wasn't often that he got to show up his flatmate, but it was so nice when those occasions arose. This was going to be fun.

He kept pressing forward, one step at a time, until he had Sherlock pinned against the door to the flat. John was careful to not touch Sherlock, just to herd him with his body, but Sherlock seemed to understand and didn't fight the attempt. A touch of pink highlighted the detective's cheeks as John grabbed the doorframe on either side of him, boxing him in.

"You look bloody gorgeous when you blush like that," John said in a deliberately low voice, keeping his eyes on Sherlock's. "You've already got those ridiculous cheekbones, so high and sharp, and seeing them with spots of color - I can't decide whether I want to snog you or slap you."

A tiny crease between Sherlock's eyebrows appeared, a sure sign he hadn't quite deduced what was going on. "John?" he repeated with a bit less strength.

John plowed on forward. "What type of lover are you, Sherlock?" he murmured. "You like it gentle, like to be petted and caressed?" He suited his tone to his words. "Or do you like it rougher?" He lowered his voice even more. "You want me to drag exactly what I want out of you, want me to make you beg for it? You would, you know - you may say you've never begged for anything before, but I can change that." He leaned in further. "I can make you crave me."

Sherlock drew in a breath. "I . . ." He faltered.

And John didn't let him take the time to regroup. "I'm so hard for you right now," he lied. Well, kind of lied - John tried not to think about how much this fun little exercise in proving Sherlock wrong was actually turning him on.

The tiny change in Sherlock's posture told John he was on the right track.

"It's too bad I'm not gay," John continued in a mock-regretful tone. "Because if I were, I know exactly what I would do."

"What?" Sherlock whispered.

John let only half of his smile show on his face, turning it into a smirk. "First, I would pin you against this door, chest to chest. You think you could avoid me? You may be taller, but I've got the advantage here - I'm not the one half-dizzy with lust." He drew himself up straighter, more aggressive, lessening the height difference between them. "I'm the one who's done this before - I could make you lose your ever-fucking mind. You're so proud of that great brain of yours, Sherlock - how do you cope when it's turned off? When your cock is so hard it aches and then you come until you can't bloody breathe? I can leave you gasping, Sherlock, not even able to remember your own fucking name. All you'd be able to think of would be me. My mouth around your cock, my hands fondling your bollocks, my fingers stroking you from inside your arse. And you wouldn't be able to do a bloody thing about it, you'd be wound so tight - fuck, that's a beautiful thought. Sherlock Holmes, great detective, naked and panting and desperate for me to pound into him and fuck him into submission."

Sherlock's lips parted and he sucked in a long breath. The color in his cheeks was even more intense, two bright spots of rose against his pale skin. John pressed his advantage.

"The fucking wouldn't come first, you know," he said, voice husky. He hadn't done that intentionally . . . this must be affecting him too . . . John swallowed the sudden hesitation and leaned in even closer, his lips a mere inch from the exposed column of Sherlock's throat.

"What do you taste like, Sherlock?" he asked. I want to suck right here." He let go of the doorframe and traced a finger lightly over the flap of Sherlock's collar, not close enough to touch skin but near enough to make Sherlock shiver. "I want to suck until I leave a bruise, a mark so everyone who sees you will know what we've been doing, what you let me do. They already suspect we're shagging, of course, but how do you think it will be once they have proof? Sherlock the slag. I think I'd enjoy every minute of it, knowing they all guessed it was me fucking your brains out." John withdrew his hand and let out a puff of breath against Sherlock's throat. "Mine."

Sherlock let out a tiny moan, which went straight to between John's legs and stayed there.

"If I were gay, I'd pin your hips back to the door here and tear open your trousers with my teeth." He drew back a bit and let his eyes dip down to Sherlock's crotch, then slowly raised them again until he could see the wonderment on his flatmate's face. "I'm very good with my mouth, Sherlock. Very good. Have you ever had someone's mouth on you before?"

A tiny shake of Sherlock's head.

"Yeah, I thought so. I can suck your bloody brain out through your cock, Sherlock, and the only thing you'll be able to do is moan. Your legs will give out and the only thing holding you up will be my mouth on your dick and my hands on your arse. Or would you prefer in?" John deliberately brought one forefinger to his mouth and sucked on it, wetting it all the way to the hilt. He drew it out slowly, eyes locked with Sherlock's the entire time, and brought it down to trace feather-light over the zipper in Sherlock's trousers. "Picture me inside you, Sherlock. My fingers filling your arse, but not enough - not quite enough -"

Sherlock's eyes fluttered closed and he moaned, long and desperate. "John -"

But then his eyes snapped open again, full of something -

He twirled away and shouldered past John's body, but not fast enough to keep John from seeing the wet spot spreading across the front of his trousers. John dropped his forehead against the door and sighed. "Sherlock -"


John wanted to put a hand on his shoulder, to offer that connection, but he sensed Sherlock wouldn't welcome it. "It's nothing to be ashamed of," he said lamely.

"That doesn't happen."

"Obviously it just did."

"I haven't done that since I was fourteen."

John adjusted his own, rather noticeable erection, and retreated to the armchair. Best to be casual about this whole thing, if Sherlock was going to have a freakout. "It's only natural, Sherlock, especially if you haven't . . . indulged in a while. I came in my pants a few times when I was a teenager too."

"Not that, John," Sherlock bit out. "I haven't done that - any of that - since I was fourteen. I wasn't expecting it to happen now."

John pinched the bridge of his nose. Life with Sherlock was constantly surprising, and yet . . . "You mean you haven't had an orgasm since you were a teenager?"

Sherlock growled something John interpreted as affirmative.

Christ. John took a moment to choose his words carefully. "Is it - do your identify as asexual?"

"I don't identify as anything, particularly."

"So - not gay?"

"Never had the inclination to find out." Sherlock gestured futilely to the spot on his trousers. "Although it looks like a possibility, wouldn't you say?"

"Do you get turned on at other times, though? Do you find particular people or situations arousing?"

Sherlock glared at him, and John reflexively threw up his hands to ward off the accusation in Sherlock's face. "Relax, I'm not trying to pry - well, I guess I am, but it's the doctor in me asking. No medical reason for this, then, just . . ."

"Just never interested," Sherlock finished for him. "Sex always seemed like it would be horribly boring."

"Yes, well now you know better."

Sherlock grunted.

"And you can admit I was right. About profanity and precision not being mutually exclusive." John snorted. "Come on, I at least deserve to hear you say you were wrong for once. That there's something you're not an expert about."

"One data point, John, and I'm not exactly a typical experimental subject."

"That's true - but that one data point supported my hypothesis, didn't it?"

Sherlock closed his eyes and inhaled deeply. "Yes, John. I suppose it did."