Why can't this work, when we both try?

She doesn't open the door so he lets himself in with the spare key they sensibly handed to him the day they bought the brownstone on Madison Ave. in New York's Upper East Side. Until recently, he had only ever used it to water the plethora of plants they (Addison, mainly) owned when the couple left town, which she claimed was futile since they were always half dead upon her and Derek's return, anyway. His retaliation was always some variation of "I'm not your house keeper," and "I had a girl with me and got distracted," which earned him a disgusted grunt and a whack on the shoulder with whatever object happened to be in her hand at the time, usually papers of some sort.

"Addison?" he calls out into the home, scanning the rooms adjoined to the foyer, "hello?" He rounds the stairs towards the kitchen, which is where he often finds her on nights like this – drinking wine ('Sipping' if he's being kind, 'chugging' if he's being honest) or disposing of another dinner left untouched. But before he can get far there is a shuffling of papers and a padding of feet and she emerges from Derek's office, eyes wide and lips sandwiched between her teeth, a panic-stricken look on her face. She relaxes a little, shoulders dropping, when he sees him.

"I thought you were Derek," she explains, pressing her back into the wall and sheepishly eyeing him.

Mark tilts his head in suspicion. "What's up," he asks, but his voice does not match the casualty of the inquiry. She shakes her head and grins one of her fake, tight grins that he has come to know so well. "Addison…" he pushes.

With a sigh of surrender she flops her arms up and down weakly, and bites her lip. "I think Derek's cheating on me," she says simply.

"What?" Mark raises two unbelieving eyebrows, "what are you talking about, Addis-" he catches a glimpse of the room she emerged from, with papers spewed about the floor and his jaw drops. He rushes in to observe the mess she has made in her search for answers and stares back at her in disbelief. "Seriously?" he gestures to the computer screen displaying his best friend's email inbox.

He can't blame her for the suspicion, he supposes. Derek has been almost unreachable for the better half of the past year. He's not angry about any violation of privacy (as long as it's not his), and couldn't care less about the current state of the room. What bothers him is that she truly believes that Derek is having an affair – judging from her glassy eyes and the flushed skin around her nose, he can tell she's been crying.

"Addison," he begins, kneeling to gather some files from the floor, "he is not cheating on you, don't be silly." Her face crumples and she cringes at his terminology. She is so sick of being called silly, or dramatic, or sensitive, or any variation of the terms.

"You sound just like him," she mutters from her place in mahogany doorframe.

"Hey, I'm just trying to help!" he snaps, throwing the papers on the desk, "I'm not a babysitter!" He regrets the words as soon as they leave his mouth, but she's already shaking her head in disbelief, bottom lip beginning to quiver.

"Did he ask you to come?" she questions through her teeth, and he doesn't know whether to say yes because although it would lower his sincerity in her mind, it would at least make her think Derek cared enough to notice she was upset when she left the hospital. He doesn't have time to decide though because she lets out a hollow laugh and disappears down the hall, with a surly "you can show yourself out, Mark."

It should count for something that he's there at all, Mark fumes as he collects the remaining papers on the floor. He's not good at being comforting, nurturing, sympathetic. He's never been one to coddle the weak and even if he was, Addison is anything but weak to him. He hates seeing her upset because he cares about her (more than he's willing to admit on occasion), but there is no instinct to humor her or indulge her in empty sentiments and tell her everything is okay when things clearly aren't. He's not going to lower the importance of her feelings for the sake of feeling useful.

He finds her in the kitchen, staring absently into her glass of wine.

"I thought I told you to leave," she doesn't turn to face him.

"Derek didn't send me, Addie," he attempts in a gentler tone, "I came because I saw how upset you were when you lost your patient. Just wanted to make sure you're alright."

"I'm fine," she replies, her voice flat.

He shifts on his feet uncomfortably. Normally this is when he would crack a joke or make a sexual innuendo to ease the tension but fortunately his verbal filter has developed since he's begun to spend more time with Addison, and it tells him this is not the time. So he asks if she wants to talk, and she shoots him a simultaneously quizzical and revolted glare.

"You hate talking," she points out.

"No," you argue weakly, "I want to. Let's talk."

"No thank you."

"Please?"

"Mark-"

"Come on-"

"What is it that you want to talk about?" she laughs bitterly, "that my husband hasn't touched me in six months? Or that he can't be bothered to let me know he won't be sleeping at home for the fifth night in a row? Or that he's having an affair-"

"He is not having an affair, Addison!" he interrupts, slumping against the counter for a second before snapping upright again when he realizes the other, more imperative point she's addressed. "Did you say six months?" he questions in disbelief.

"Six months and eight days, if we're being precise," she mumbles into her glass and raises her eyes to meet him. She almost looks ashamed, he recognizes. He pours himself some wine.

"That's, a long time," he chokes, but quickly alters his tone when he sees her miserable nod, "but everyone goes through dry spells, you're both so busy." It sounds so scripted and cliché, but it's the best he's got. He's Mark Sloan, and he's pretty sure he hasn't gone more than a week without sex since he began having it sometime in the tenth grade. The idea of taking six months off isn't something he can empathize with.

But, he would be lying if he said he wasn't, on some level, pleased with the fact that she hasn't been screwing his best friend lately.

"Fuck you, Mark," Addison sneers, and it's clear that she's drunk because she doesn't curse unless she is. Drunk or very angry, and right now it's both.

"That's always an option," he winks.

"You're incorrigible," she wrinkles her nose, "and that's adultery in case you didn't realize."

She reaches for the bottle of cabernet and pouts when no liquid swishes around inside and he has to smile at the sight.

"I think it would be more like an act of service," he muses, pouring some of his wine into her empty glass.

She laughs, and it's seemingly more genuine this time, "What makes you think, if I decided to venture out onto the path of adultery, that it would be with you?"

She points a thin finger at him playfully and he seizes it in his grasp, "because," he explains simply and flutters his eyelashes, "then you can claim to have just fallen victim to my irresistible charm."

"You're full of yourself," she observes and he resists making a highly inappropriate comment involving her being full of himself instead. "Besides, I think I made it clear that your charms have no effect on me, years ago." She alludes to their internship at Mt. Sinai and his many failed attempts at courting her.

"Yes, you sure did," he agrees, finishing the red liquor in his glass.

He won't lie about his intentions in those early years – he was not in love with her, and perhaps the driving force in his continuous attempts to get her into bed was the fact that she didn't fall for any of his stunts, never hesitated to call him out on his bullshit, and pointedly expressed her dislike of his character. Maybe he wanted her because he couldn't have her, and maybe he was always inherently in competition with his best friend. So maybe she was right to pick Derek, who knows. But as he looks around the desolate house and the redhead poignantly tracing the rim of her glass with her pinky, he wishes she had given it just a little more thought.