Disclaimer: Grey's Anatomy is the property of Shonda Rhimes and ABC. This writing is for entertainment purposes only and is not for profit.

The lights are dim in the plush hotel room, drowning them in just enough darkness to match the mood and see each other at the same time. They're on the bed, he's on his back, and she's on all fours over him. Their lips are totally fused, not even parting to breathe, choosing lightheadedness over separation. When they absolutely need to, though, it's a quick breath before they dive into the kiss again, mouths open and fervent.

Mark's hands rove about Lexie's body over her clothes, and they settle on the backs of her thighs, at the joint where her legs meet her buttocks. He unconsciously squeezes and rubs them alternatively, mindless, a reflexive action. She rests more of her weight on him, teeth grazing his bottom lip. Her bare feet rub against his socked ones, burrowing in their warmth. He feels the gentle curve of her smile against his mouth and it's just the way it should be.

It's a routine that never changes; but it never needs to because it never gets any less enjoyable.

When they stop kissing, Lexie doesn't stop moving. She slides backwards, palms skimming down his bare chest and across the waistline of his jeans.

But, suddenly, everything's different and incorrect, a big pink elephant making its way into the room. Mark doesn't enjoy it as much as he usually would. It's happening again: a sudden attack of guilt washes over him like an ocean wave. He opens his mouth three times to say something, but he can't quite find the right words. Finally, on the fourth try, he grasps something through the fog.

"Sometimes I feel…"

He has to a pause for a groan and breathy expletive when she runs her hands along the triangle where his thighs meet his groin, purposely ignoring the bulge in his crotch, to torture him. And god does she know how to do that (somehow she always has). He closes his eyes and takes a deep breath to regain his bearings.

"Sometimes I feel like a dirty old man."

It's not the first time this has come up, and not the first time recently, either. He knows how stupid he sounds. He's inventing issues, making up problems. Ever since the whole Derek thing blew over, there have really been no roadblocks in their developing relationship. No more keeping secrets, no more angst between friends, no more Romeo and Juliet stuff.

Everything is sickeningly perfect. It's uncomfortable for him. He's really not used a relationship without conflict; it's just one of those things he can't fathom.

So he reaffirms his semi-imagined concern, frowning, speaking gruffly. "You're so damn young, Lex." He glances up at her, blue eyes uncharacteristically self-conscious.

Her mood successfully murdered, Lexie lets out a ragged sigh and runs her fingers through her dark hair. She kneels on either side of his stomach, looking down at his torn expression with a mixture of sympathy and frustration. "Mark," she says, cupping his face in her hands, "you know that doesn't matter to me."

She's made that point clear, again and again, every single time he's brought it up. And, frankly, it's getting a bit old now.

Mark grunts. "Still, it bothers me. It's like I'm taking advantage of you. Like a sleazy high-school teacher or something. One of these days, I'm expecting Chris Hansen to confront me in an on-call room while I'm waiting for you." The comment should offend her a lot more than it does, but she can see that he's still struggling with the age difference between them. She knows he's right, that it's a large gap to bridge, but she hasn't had any problems with it so far.

"I guess I don't understand where you're getting all this from," she tells him honestly, eyes dropping to the side, disheartened at his reluctance. Everything has been going so well, and she wouldn't be able to stand losing what they have over something like this. "I mean, yeah, I'm a lot younger than you. But we're both adults. We both act like adults."

Even in the low light, she can see him deadpanning. "You drink from a juice box. You skipped the third grade, so you're even younger than your tater tot-loving pals," he lists slowly, counting on his fingers. "You stammer and get all flustered when I make a crude comment, which is adorable but makes me feel like a predator. And, most importantly, you showed up at my hotel room and did a striptease while demanding that I 'teach you.'" He swallows the intense desire that manages to rise from the memory. "I think that's reason enough to feel the way I do."

She listens to his points and gives them each careful consideration. Then, she narrows her eyes and crosses her arms across her chest, ready to counter. "Okay," she begins. "First of all, juice boxes are delicious, nutritious, and low in calories. Better than water, that's for sure. I skipped the third grade because I was more mature and capable than the others in my class, and I like to think that it's the same with my intern class. Next, when you say those dirty dirty things to me, the reason why I blush and stutter is because I'm imagining that whatever you said actually happening." She has to laugh, then, a light sound with a nervous quality to it. "And trust me, some of the things you say would make absolutely anyone blush."

"What about your need for lessons?" he asks, raising an eyebrow, pursing his lips. She bites hers and rolls her eyes to the ceiling as though the answer is written there.

"Yeah." She laughs once. "That…it wasn't me. I had never done anything like that in my life," she said contemplatively. "I guess I was just trying to tell you what you wanted to hear. You do refer to yourself as a guru, you know."

Mark chuckles half-heartedly. "Yeah, well." He doesn't finish his statement, and silence falls over them for a few moments. Their eyes don't meet, deliberately averted.

"You know," Lexie says quietly, finally meeting his gaze and forcing him to meet hers. "when I look at you, I don't see an age anymore. I don't see the fact that you're an attending and I'm an intern. Besides, it's not like that kind of relationship has never happened before."

It's a point that Mark can't contradict. He keeps his mouth shut.

"You're right, I am young," she says, nodding, assertive. "But I'm no nymphet, and you're no Mr. Humbert. I can make my own decisions and my own mistakes." She smiles at him, with teeth, placing her hands firmly on his shoulders. "And I chose to be with you. I chose to be with you, Mark Sloan. Regardless of your age, not because of your title. And if making that decision ends up being a mistake, then it will be one that I willingly went into."

It's an uneasy thought. Silently, they both hope that's not and will never be the case.

"So I'm not creepy?" Mark asks after a moment.

Smiling softly, Lexie shakes her head and presses a kiss to his lips. "No."

"I'm not a dirty old man."

Another kiss. He weaves his fingers through the dark hair at the nape of her neck.

"No."

"And you're in this?" It's completely unrelated to the issue at hand, but still a concern in and of itself.

"Yes."

At her sure and steady answer, a weight is lifted, and Mark finally finds it in himself to smirk. "And you'll never show up here wearing a slutty Catholic schoolgirl uniform?" He waggles his eyebrows before breaking into laughter.

Lexie giggles, blushes, and hits him playfully in the arm. But, then, a sudden change: her gaze transforms into one that's dark and intense, focusing directly on his eyes and piercing him with sensuality. Her voice is an octave lower than usual as she leans in close, mouth grazing his ear, and says, "Not unless you want me to."

Her hand slips quickly beneath his jeans and boxers, and, with a gasp, he hates her and adores her and wants her so badly at the same time.

It's a feeling suspiciously like love, but Mark can't say that yet. Neither of them can.

For now, they can only feel it.