Author's Note: Sorry about the lack of updates, you know the normal excuses and the million and one single-shot fics running through my head. I'm fast-forwarding about two weeks with the timeline, love quadrilaterals and the tension that comes along with them take a bit longer than a day to develop. As always, enjoy and review.

Disclaimer: I do not own these characters.

Meredith sips her diet coke as her eyes scan the crowded lunchroom. It's been two weeks since she's started her internship.

Two weeks that seems a lot more like two months. Meredith has never been more tired in her life. She'd like to blame the job, but she knows it could very well be the fact that she and Derek went down to the harbor to see the sun rise three out of the past five nights.

Mark joins Meredith at the table, and interrupts her thoughts.

"Hey you," she says as she sets her soda on the table.

"Hello, Dr. Grey," Mark says, feigning seriousness, as he stabs at his salad with his fork.

"Dr. Sloan," Meredith nods. "Having a good day?"

Mark sighs as he rests his fork on his plate and leans back in his chair. "My day is going alright, but I'm completely exhausted."

"I know the feeling," Meredith responds.

"Oh really?" Mark laughs. "I hardly see you around here anymore."

"I'm around, you're the one that's been M.I.A."

Mark shrugs, "If only that was really the case. So Bailey has you back on scutt work?"

"Yeah, back to being a normal intern. I guess sleeping with the boss could only get me so far. Cristina's happy that I've joined her in her misery."

"You're enjoying every second aren't you?" Mark leans forward and resumes eating his salad.

"What can I say? I'm a masochist."

"We all are, you're not the only one in that boat." Mark replies not realizing that his words carry more weight that he intended for them too. His thoughts shift to Addison, and he tries to redirect his attention back to Meredith.

"You okay?" Meredith asks.

"Yeah, just tired."

"Well if you aren't too tired, or busy maybe we could grab a beer tonight, you know do the whole catching up thing. You can tell me about the new woman in you life."

Mark drops his fork. "What makes you think I have a new woman in my life?"

"Well, lately you've been tired, unfocused, and your inappropriate, pervey comments aren't as frequent. All things that lead me to conclude that you have a new woman in your life."

"Grey, you couldn't be more wrong."

"Am I?"

"Well I guess there is someone, but you could hardly call it a relationship or anything like that."

"Seriously?"

"Yeah," Mark replies leaning back in his chair, completely giving up on finishing his lunch.

"Good for you, finally making some attempt to move on."

"What is that supposed to mean?"

"Nothing." Meredith says as she takes the last sip of her coke. "Nothing at all."

Mark begins to defend himself when Meredith's pager begins to go off. "Damn, I have to go answer this." Meredith moves to stand up. "Seriously I'm happy for you. If not tonight, we really should get a drink sometime."

"Definitely. I'll see you later Dr. Grey." Meredith smiles at him as she picks up her tray and goes to answer her page leaving Mark alone with his thoughts.

-x-

Addison walks down the cool, tiled hall. With each step her heel makes a clicking sound that echoes through the hallway. She knocks Mark's office door, softly, waiting for an answer.

She's been an adulteress for two weeks now, and she's still waiting for the guilt to sink in. It hasn't, and that in its self makes her feel guilty—Guilty about the fact that she doesn't feel guilty. Addison tries to silence her thoughts and remind herself that she thinks too much.

She always thinks too much, Derek used to tell her it was cute. Now he just tells her he's too tired to deal with it.

Addison feels a hand wrap around her waist, which causes her to jump.

"Damnit, Mark, you scared me!" Addison scolds as she turns to face him.

"Did I?" Mark asks mischievously keeping his hand wrapped on her waist.

"Yes." Addison pushes Mark away, and takes a few steps backward. "We're in public." She whispers softly.

"I know. I'm kind of observant in that way." He smiles and leans forward and kisses her just to piss her off.

"Mark," she hisses.

Mark kisses her again and pushes her against his office door. "What would you do if I decided to take you right here. Would you tell me no?" his whispers, hoarsely in her ear as he begins to run his hands along her sides untucking her oxford from her tailored skirt.

Addison feels herself give into Mark's touch, and silently curses herself for being so mentally weak. Mark makes her feel wanted, and loved, both of which she hasn't felt in a long time.

She weakly attempts to free herself from Mark's weight pinning her against the door, but fails as Mark begins to place small kisses along her collarbone. "Do you want to get caught?" She moans trying to hold onto what is left of her fleeting self-control.

"Don't you?" Mark releases his grasp on her waist and steps backwards, leaving Addison breathless against the door. She glares at him obviously quite flustered. "Are you still coming with me to the fundraiser tonight." Addison asks as she attempts to regain her composure.

"Always."

-x-

Mark shoves a file off his desk into his bag. He looks down at his watch and realizes he's running late. He hurries out of his office and waits for the elevator.

"Hey," Derek says as he walks up to him. "You're getting out of here early."

"Yeah, Addison has that thing she wanted to go to tonight, and I told her I'd take her."

Derek shifts uncomfortably. His own discomfort causing him not to notice that his best friend is avoiding his eyes.

The elevator arrives and the two friends step in. "I've been meaning to talking to you about that." Derek says, leaning against the wall in the elevator pressing the button for the main floor as well as the surgical floor.

"About what?"

"Addison. You're not blind, you can tell things are rough, and have been for a while now, and I just want to thank you for taking her out, and what not, it makes things, well, easier for us."

Mark feels a sinking feeling in the bottom on his stomach. He looks up at Derek, unsure of what to say.

"You guys will get through this," Mark replies.

Derek runs his hands through his hair. "You know, I'm not so sure about that anymore."

Mark exhales as the elevator reaches the main floor and the door opens. He sees Addison waiting for him in the lobby.

"Goodnight," Mark says as he steps out of the elevator.

"Goodnight," Derek replies his eyes meet Addison's. He gives her a small smile. The elevator doors close, Mark walks toward Addison feeling more guilt with each step he takes, but not enough to make him turn and walk the other way.

-x-

"You're being ridiculous." Meredith informs Derek, as they walk through the hospital parking lot.

"No, I'm not. It could happen, post-op patients need constant observation."

"And for that reason there are other brilliant interns, and doctor who are on-call that can provide this 'constant observation.'"

"But none of them are quite as brilliant as you, or any where near as humorous."

"So you want me to stay on-call so I can make you laugh," Meredith rolls her eyes. "Goodnight, Dr. Shepherd." Meredith and Derek stop walking as Meredith opens the door of her Jeep. "Go home, get some sleep. You're not even on call tonight."

"I know." Derek replies not having the energy to formulate a snarky comeback. Silence fills the cold, night air.

Meredith leans against the Jeep door and begins to feel a bit uncomfortable with the way he's looking at her combined with the fact that he's only standing a foot or so in front on her.

"Goodnight, Dr. Grey." Derek leans forward and kisses her softly on the lips before he even realizes what he's doing. Derek walks away from Meredith and the car. Meredith gives him a sad smile as she climbs into the Jeep.

"Goodnight, Dr. Shepherd."

-x-

Derek cannot escape his thoughts on his drive home. He had kissed Meredith Grey. He crossed the line that they flirted with so dangerously for the past two weeks. He cannot actually believe he had the audacity to cross that line.

He pulls into the garage and climbs out of the car. He looks down at his watch, realizing it's still early and that Addison would still probably be out with Mark.

He turns his key in the lock and walks through the laundry room to the kitchen. He checks the stack of bills on the counter, sticking a few of which in his bag.

He walks from the kitchen to the main foyer. He begins to walk up the stairs to his bedroom, relieved that Addison isn't home and that he has the grandiose, empty house to himself even if just for a few hours.

He walks down the hallway leading to the master suite running his hand along the walk, careful not to run it into the one of a kind painting that adorn the neutral painted wall. Addison always told him that he dirtied the halls because he was constantly rubbing them with his hands. He always rolled his eyes and ignored her. He knows you have to pick your battles, and lately he's chosen not to pick any, it's just easier that way.

He turns the handle on his bedroom door and pushes open the door.

Addison's head is thrown back in ecstasy, as she appears to be riding another man, who bears a sticking resemblance to Mark. Derek stands there motionlessly for a moment not able to fully comprehend what he's seeing and exactly what it means.

"Oh my god," Addison cries as she notices Derek standing there. She pulls the sheet to her chest. She moves out of the way allowing Derek to get a better look at the man who is responsible for his wife's pleasure. He feels a sharp pain in his side as he realizes the man is Mark.

Derek turns and closes the door behind himself. He walks out, the same way he came in, running his hand against the wall the entire way.

-x-

Meredith opens her front door and is completely taken aback to find Derek standing on the other side. His face is red, especially his eyes. His hair is disheveled.

"Derek…"

"I need somewhere to sleep." Derek pauses. "Please?"

Meredith opens the door further. "Okay."