A/N: the title is taken from First Time by Lifehouse.

"So . . . dirty sexy-sex?" Lexie's eyes glint a little, eyelashes creeping upwards as she smiles.

She's drunk. Granted, she's a cute drunk. But she's drunk and Mark's kind of not. He's the driver tonight: when he drives her, he takes it seriously.

"Dirty sex in Joe's bathroom." There's a thrum in her voice that translates into a tightness in his balls. He wants her (it goes without saying) but he doesn't want her in Joe's bathroom and he doesn't want to talk about why. The whole subject makes him feel dirty - in a bad way.

"We have a bed, Lex. Why don't we just go home and use it?" He just stops short of sighing.

"Because . . . " She puts her head on one side, ramping up the cuteness factor. "I want to have dirty bathroom sex at Joe's with you."

"We also have a bathroom." He glances around, because her voice isn't exactly quiet. "How about the shower, huh? I'll do that thing you like," he bargains. He's smirking, but it's half-hearted. "You know, the thing where you -"

"You could do that in a bathroom stall," she argues, reasonably enough, because long and varied experience has proved that he can. "Please?"

"No," he insists. "I'm not having sex with you in a dirty bathroom." He stands up and throws some bills down on the bar. "Come on, Lexie."

"No!" She smiles, drunkenly triumphant. "You don't understand. Not dirty bathroom! Dirty sex!" Then she sways a little dreamily, a faraway smile on her lips, swatting a hand lightly against his arm. "Dirty sexy-sex."

"I got the idea the first time." Mark lets himself smile a little - the bizarre, inebriated Grey-speak (dirty sexy-sex for the love of God!) is stupidly charming (it's the way she says it and just the fact that it's her) and kind of turning him on. That and the pink flush on her cheeks and the way her fingers are trailing down his hip. "Come home with me, huh?"

Drawling in her ear usually works pretty well, but this time she just scrunches her face into a demand. "Why won't you have sex with me in Joe's bathroom?" She pouts a little pout. "I've never had sex in there. I'm probably the only person at Seattle Grace who hasn't."

Joe, a few feet away down the bar, raises an eyebrow that half sympathizes, half warns Mark to quieten her down and stop advertising that his friendly drinking establishment is really nothing more than a seedy hook-up joint.

"Okay." The word is a slow rasp in Mark's throat as he leans in, stroking her arm. He's getting hard now and the prospect of the bathroom seems more and more inviting and less and less about misgivings. "Go to the ladies' room and I'll -"

But she's drunk: she doesn't register the change of heart or hear his words and she just plows on.

"What's more I'm probably also the only person at Seattle Grace who hasn't had sex in Joe's bathroom with you!"

And there it is. Hole in fucking one. The reason he wanted to take her home in the first place. He's changing for her. More than that, he's changed. But he's screwed more women in Joe's bathroom (and other interchangeable facilities) than he can reliably recall (or wants to try to). The fact the Lexie chose to remind him of that only makes it more cringe-making.

"I'm pretty sure I turned Richard Webber down," he mutters. "Maybe I should buy him a drink sometime - see if I can't put that right." He turns his back and walks away a few paces. "You coming?" It comes out like he doesn't care one way or another, but he's just hurt and embarrassed and he's hoping that the sixth sense she seems to have for him will register that.

She doesn't even acknowledge the question. Just narrows her eyes and says, "I'll bet you had sex with Callie in there."

He raises an eyebrow sleazily, indicating that he did. Insecurity about him and Callie is Lexie's Achilles heel. Since she's rubbing his raw right now, it seems like poetic justice to bruise her feelings. But really he only makes himself feel even worse, while she just stays pissed off and petulant as she crosses her arms and abruptly turns her back.

"Fine," he says. "Get Joe to call you a cab."

He's almost reached the door when he feels a warm touch against the sleeve of his jacket. She's there, looking up at him, still a little pissed, still adamant, but there's something soft about her now.

This time all she says is, "Please. Fuck me."

He wants to look after her. Wants to make sure she's comfortable, that the toilet roll holder isn't sticking into her back (which it is); that she's not standing in something gross (he avoids looking at her left foot and the half-shredded damp paper stuck to her shoe). But he knows that's not what she wants.

She's three sheets to the wind and she wants Mark Sloan, rough and up against the wall. The manwhore she never quite got to meet.

Her breath is hot against him and her hair's all messed up. Her cheeks are flushed almost red now, partly from drinking and partly pure lust. Her hands work his belt undone and go for his zipper and, when she pulls it down, the sound seems impossibly loud.

His blood is pounding now. His body doesn't give a shit about new leaves or integrity or making everything with her different. He's hard and she's wet and, yeah, she's right, he's done this so many times he has it down to an art form.

He lifts her butt a fraction, angling her hips and she hooks one leg around him, the foot pressing into his calf. He kisses her, tongue in her mouth, lips hungry, sharing saliva as his hand pulls her panties down and he pushes inside her.

When she shudders, he groans. When he thrusts, she begs for more. There's nothing about this that's gentle. He's inside her, hard and deep and his fingers are firm, abrasive, taking her to the edge.

She moans when she comes and he covers her mouth with his, silencing her, tasting her, pushing her back into the hard wall as he climaxes.

But it's not the same. He knows how this goes and this is so not the same. You get off in bathrooms - quick, dirty, simple, meeting your needs - and this is so much more than getting off. It's like this hot ecstasy of pleasure where he's part of her and he feels her and he knows, better than knows, that he loves her.

Knows that she loves him.

He opens his eyes, barely understanding what hit him and she's smiling so hard it does something to his heart he'd call breaking if it didn't feel so good. He'd smile back (she's contagious that way) but he doesn't really have control over his facial muscles. He's screwed so many women in bathrooms. So many women, period. But even when everything's the same, just being with her makes it different.

"Was that so bad?" Lexie asks coyly. She's still a little drunk and she's looking for a compliment. But she's glowing and she's with him and she's watching him like he's the only sight on earth she really wants to see.

Mark stands over her, braced against the wall, surrounding her, looking into her eyes. He still can't really move, but he just about manages to shake his head.

"It was okay, though, right?" She's teasing, but still just a little unconfident. "Dirty bathroom sex with me wasn't so bad?"

He brushes her face with the back of his hand, lightly, feeling her skin. He doesn't quite trust himself to speak, but finally gets out, hoarse and deadly serious, "I never did that before." He swallows. "I never did it with you."

For a moment, she's held in his eyes. She gets it; she felt it too. Then a wicked little smile turns up the corners of her mouth. "Want to go again?" she whispers.