A/N: Okay, quick back story on this. It's AU, first of all. It's set in present time, but Addison, Derek and Mark are in New York. Addison married Mark five years back. That's about all you need to know- the story will tell the rest. I don't think this will be more than a one shot, because I've already started abandoning my other ongoing stories. Anyway, enjoy.

Time to say goodbye.

Paesi che non ho mai (I'll go with you to countries I never)
veduto e vissuto con te, (saw and shared with you)
adesso sì li vivrò. (Now, yes, I shall experience them)
Con te partirò (I'll go with you)
su navi per mari (on ships across seas)
che, io lo so, (Which, I know)
no, no, non esistono più, (No, no, exist no longer)
it's time to say goodbye

"I'm fine." She said, averting her eyes towards the ground.

He took her hands in his and gave her a knowing look.

"Okay, so maybe I'm not fine." She sighed. "But it wasn't his fault-"

"Wasn't his fault?!" Derek exploded, dropping Addison's hands to her sides. "Addison, you did not bring this on. Stop making excuses for him! It's been five years, Addie, five years. We both know that he hasn't changed any, and you can't keep letting him do this to you over and over again."

She looked him in the eyes for the first time since he knocked on her door, and he could finally see the hurt she'd been trying to shield all evening.

"You know what, Derek? I'll be fine. Just…go home. Mark might come home soon anyway, so I might as well talk it out with him if he does…"

"Addison. You called me an hour ago crying. You aren't fine, and I'm not leaving you here for that bastard to come here and tell you that you brought it on yourself."

She sighed and sank down onto the couch, tears threatening at the corners of her eyes. Derek sat down next to her and took her hand.

"Addie, the truth is that he doesn't deserve you. No one deserves to be cheated on, and especially not you."

"Sometimes," she started, "I look in the mirror and ask myself what's wrong with me. What did I do that was so unthinkable? I've worked five years trying to make him happy, and nothing I do is ever good enough. I've doubted my marriage since it happened, and I just…don't know what he wants from me."

"He wants you to be this perfect person Addison, someone without feelings he can hurt or a heart to break. If he doesn't accept you for you, then you should find someone who will."

Addison closed her eyes and took a deep breath, nodding. "I know." She said, and they sat there in silence.

"You know," she said, breaking the stillness of the conversation, "you're the only person who hasn't tried to make me something I'm not. You don't hold me up on some pedestal and force me to change who I am. That's…what keeps me sane, Derek. Thank you for that."

She looked at him, and for the first time in his life, Derek didn't give a damn about what Mark thought. He'd been fighting his feelings for Addison for years, and he kept them a secret for Mark. Mark, who he'd called his best friend. Mark, who broke Addison's heart.

Both of them seemed to be lost in each other's eyes at that point, and before Addison knew what was happening, her lips were on Derek's and they were stumbling towards the bedroom.

"Addison?" Mark called into the house as he stepped in. It was dark, except for the lamp in the living room they always left on.

"Addie? Are you home?" He saw a light peeking out from the door of their bedroom, and as he walked down the hallway, a flicker of reflected light caught his eye.

Oh, God, no.

There, on the coffee table, were Derek Shepherd's car keys.

No. No, no no. This isn't happening.

He threw open the door, and instantly saw the thing he'd been fearing for years was right in front of him.

"Mark!" Addison shrieked, hurrying to cover herself with the comforter as his face changed from an expression of shock to one of rage, standing with clenched fists in the doorway.

"Mark." Derek said, barely above a whisper. "Damnit."

"Bastard." Mark said, his voice coming out low, angry and full of the hate that flickered in his eyes.

In an instant, he was storming down the hallway, slammed the front door behind him, and sped off into the night.

Addison laid back on the bed, sighing.

"Oh, my God."

The next morning, Addison stood at the nurses' station, reading a file. She could feel everyone's eyes on her as she placed the file back and started down the hall. It was eight hours later and already, everyone knew.

I just need to get through the day. Ignore everyone.

She heard interns talking excitedly in the corner of one of the halls as she passed.

"Amy! Get over here! Two of the attendings are fighting!"

"Which ones?"

"Shepherd and Sloan!"

"I thought they were best friends!"

"Apparently, Sloan came home and found Shepherd in bed with his wife."

"Oh my God!"

"I know, let's go!"

The two young doctors rushed out and were suddenly face to face with Addison, who looked horror stricken.

"Oh…doctor…Montgomery."

Addison hadn't changed to her married name. They'd talked about it, but "Addison Sloan" never sounded quite right.

She rounded the corner, ignoring the stammering interns.

The second she saw them, her breath hitched in her throat. They were screaming at each other, half the hospital as their witness.

"You seduced my wife!"

"You cheated on your wife! Again!"

"I was coming home to try and work it out!"

"Guess you were a little late, huh?"

Addison took a deep breath and walked into the scene, shaking.

"Stop. Both of you, just…stop."

"You expect not to kill him?!" Mark erupted, giving her the same look he had last night.

"We were having problems long before this happened, and you cheated on me first, multiple times. You wanted me to be perfect, Mark, you wanted to change me. I'm not going to let you bring Derek into this, because this was not his fault. It was mutual."

"Addison-"

"No! You don't get to do this, Mark! You don't get to stand here and be angry, because you have no right. No. Right. I've been waiting for you to care the least bit about me for five years, and nothing about you ever changed. I should have seen it coming, I should have realized…" She shook her head, "You're never going to change. You've been cheating on girls your whole life, why should I be any different?"

She stormed out, running to an empty on-call room and slamming the door. A few minutes later, the door opened.

"Derek." She said, her voice hoarse.

"Addie, I'm so sorry about all this. I shouldn't have let us do that last night, I should have-"

"No, Derek, I wanted to. I could have stopped you, but I didn't. This isn't your fault. Mark brought this on himself. You helped me realize that I was making sacrifices for him, and I refuse to do that anymore."

He walked over to where she was sitting and extended his hand.

"Come on. We need to get out of here."

She nodded, taking his hand and managing a weak smile.

"I can't face these people anymore. I need…I need to be anywhere but here."

Mark walked through the hospital the next morning. He'd spent the night in his car, which seemed like a good idea at the time, but had caused back problems and a worse mood than before. He hadn't seen Derek or Addison all day, and he'd like to keep it that way.

"Mark." He sighed. Speak of the devil.

He turned around to find himself in front of Addison, wearing her coat and holding a golden envelope.

"Here." She said, holding it out to him.

"What is this?"

"Open it."

He reached inside to find a box, a piece of paper, and a smaller envelope. She watched him as he looked at each thing.

The paper had a name and telephone number written in Addison's handwriting.

"He'll be calling you, soon."

He looked puzzled, but continued.

The envelope had Addison's house key.

As he went to open the final box, he realized who the name and number belonged to. Addison's lawyer.

In the box, her wedding rings.

"I called Richard Webber last night. I'm transferring to Seattle Grace."

Mark looked from the rings in his hand to Addison and back again, then finally spoke.

"So this is it? This is how we end this?"

"It's all that's left, Mark. We've been fooling ourselves."

He watched her walk out the door of the hospital and to a car that wasn't hers. When the driver's side door opened, his fists clenched.

Derek had stepped out and they were talking. Mark tried to read their expressions.

She said something and smiled. He took her hands and smiled back, then pulled her into his arms. He opened the car door for her and then got in himself, and drove off.

He thought about what had just happened, and suddenly, horribly, realized what was going on. He reached into the envelope and when he felt it, he knew.

There, in his hand, were papers from a copy machine.

Derek's transfer papers to Seattle Grace.

A/N: So. Random. Whatever. The lyrics are from "Time to say Goodbye" by Andrea Bucelli and Sarah Brightman. I love that song- we used it at my great grandma's funeral. I translated the lyrics from Italian, so it should make a little sense. I don't know, the tone seemed right if you listen to it. Again, this is a one shot. And in case you didn't catch it, Derek and Addison are ditching McAsshole in New York and going to Seattle to live happily ever after.