A/N: Ok after much consideration I have decided to go off on an AU tangent. I think Addison and Mark have been through enough. I hope you will like it. . This is the Chapter where Derek finds them in bed together. Please review and let me know what you think.
Addison called Derek and reluctantly agreed to go to the Dinner at the Chief's house as one last favour to him. She felt it was the last thing she could do to help him, then she could be free to start her life again. Mark was not overly impressed with her decision but he respected it. After all she wouldn't be the woman he loved if she didn't care so much for her friends, and as messed up as the situation was Derek and Addison were friends.
The Dinner was boring just as she had expected but she knew how to play her part. She wore a simple black cocktail dress with her hair tied up, immaculate makeup and killer heels her trademark. Addison smiled in all the right places said all the right things, 1 year of finishing school her father insisted on paid off in situations like this.
Derek played his part too as the attentive loving husband. If only they knew. After all of the goodbyes were said, Derek insisted that Addison come back home at least for the night so they could talk.
"Ok, can you stop the silliness now and come back home? You have made your point. I will try to be a better husband but you have to stop being so selfish and petty" Derek said
"I'm sorry I just can't do that" Addison replied
"You can and you will"
"Derek, come on let's be honest with each other, you don't want a marriage like this anymore than I do. We just fell out of love"
"Fell out of love, please what has happened to you? You were never THAT GIRL, the needy soppy romantic girl that needed soppy words, that was what attracted me to you in the first place"
"Well Derek, perhaps you just never took the time to get to know me. That is partly my fault I never let you know the real me. After 10 years of marriage there are so many things you don't know about me."
"Like What?"
"It's too late Derek, we are over. I'm sorry it has come to this but I need to go"
"You know what Addison, go, calm down, and have your melt down, maybe visit Naomi and Sam in L.A get some perspective then come back. When you get back to your normal self we can get back to our normal lives"
Addison left and went back to her hotel. It was late but she knew Mark would be worrying about her so she called him to let him know she was safe at the Hotel and that they would catch up the next day.
3 days later Mark received a call from Addison. It was a Saturday evening and Derek was at the hospital yet again another emergency.
"Hey Mark" Addison said
"Are you ok? You sound a little flat"
"I'm Ok, can you come over to the brownstone. I need your help"
"What are you doing there?" he asked exasperated
"I'm just... Please just come over, it's a surprise, I think you will like it" She said smiling "At least I hope you will"
"Alright, I'll be over in 15 minutes"
True to his word he knocked on the door, and let himself in.
"Addie" He called out
"I'm upstairs" she called out.
Mark made his way upstairs and smiled when he seen Addison packing all of her belongings into various bags.
"Is this what I think it is?" He said smiling
"If you think it is me packing all of my things to finally get out of this house, then you would be thinking correctly.
"Oh baby, finally" he said taking her in his arms.
He pulled back a little to look at her beautiful face and gently kissed her. He deepened the kiss and began to let his hands wander over her body. She moaned at his touch. She couldn't get enough of this man. Her whole body tingled and ached for him, as hers did for him.
She stopped him. "Hun let's get this stuff into the car and then we can get out of here"
"That sounds like a plan" He said kissing her again quickly.
"I'm not worrying about any of the big stuff; Derek can keep all of it. I just want to take a few personal things and what is in my office, which I have already packed up, so if you want to take that to your car I'll finish up here with all of my clothes"
"You do know that I haven't got a truck." She said with a smirk, referring to all of her clothes.
"You're so funny" She said sarcastically "Really it's a good thing you are a Doctor because I don't think you could make a living out of being a comedian" She said playfully
"Hey I make you laugh, I must be doing something right" He replied
"Yeah well you have to laugh at your boyfriends jokes don't you?" she said
"Boyfriend. Do you have any idea how good that sounds" he said
"It does doesn't it. Now go so we can get out of here"
An hour later just about everything was packed in the car and he came back into the bedroom to pick up the last suitcase.
Mark came up behind her, put his arms around her stomach and she leant back into his chest. He pushed her hair to one side so he could start to kiss her neck. He moved his hands up to her breasts and began to caress them.
Addison turned around and kissed him full on the lips. She couldn't resist him and before either of them realised what they were doing clothes were being removed and they were falling onto the bed.
Mark ran his hand down the outside of her leg and then back up the inside of her leg, until he reached her centre that was already wet with anticipation. She moaned as his mouth began licking and softly biting her nipple. Addison ran her hands over his back.
"Now Mark please" she breathed
He could never deny her anything she wanted especially in the bedroom, even if this wasn't their bedroom; he entered her slowly before they found the perfect rhythm. Addison wrapped her legs around him and began to gasp as he moved so expertly inside her.
They were both so oblivious to anything other than what they were doing that they didn't hear the front door open. Derek was tied he had to get some sleep he had been at the hospital for 18 hours and had to tell a family that their son didn't make it. It had been a rough night. He had no idea it was about to get even rougher.
The house seemed quiet yet he knew Addison was home her handbag was on the hall stand. Something felt a little off, he couldn't put his finger on it but something felt weird. He made his way upstairs; as he approached his bedroom he could hear sighs and moans. He gently pushed the door open and was greeted by a sight he knew would stay etched in his mind forever.
Addison saw him first. "Oh my god Derek" She said.
Mark turned around, removed himself from Addison and tried to cover them.
"Derek, I'm so sorry" Addison said
"SORRY! SORRY!' was all Derek could say as he turned and walked back down the stairs.
Addison and Mark quickly pulled their clothes back on and ran downstairs to see Derek pacing in the entry way.
"My god Derek, I'm so sorry, you weren't meant to find out like this" Addison said
"Like this! How long? How long have you been screwing my best friend behind my back?" Derek exploded as he grabbed Addison by the wrist.
"Don't touch her" Mark exploded
"Don't you dare even talk to me Mark? How could you?"
"Look I'm sorry. We both are. We didn't want you to find out like this."
"What do you mean like this? I'll ask again how long have you two being screwing each other behind my back? Is that why you want to separate Addison so you can be with Mark? Oh this is just perfect" He spat
"I'm so sorry Derek is it really that important how long?" Addison asked
"Well that says it all obviously a long time. How can you be so stupid? Mark wants you because he has always wanted everything I've had. You are just another one of those things Addison"
"Shut up Derek, that is not true. I am in love with her. I always have been. I have stood by and said nothing for years. I have watched you ignore her and treat her with indifference for years now."
"So you took advantage of that. You are a son a bitch you know that"
"That maybe true, and I deserve you being angry with me, but admit it you have been in a lousy marriage for years now and Addison deserves to be with someone who loves her, someone who will make her happy. Which I'm sorry Derek you just don't do"
"Mark please stop" Addison said
"Oh look at that she is defending you now. Addison I can't believe you are stupid enough to believe he loves you. You are just another notch on his belt. He will toss you aside once he has tied of you and I will not be here to take you back." Derek said vehemently
"Derek please, I know you are angry right now with every right, but Mark and I... well its real. He isn't going to leave me"
"Just get out both of you. I never want to see either of you again"
"Derek, I know you're hurting but it doesn't have to be like this" Mark tried
"I said Get out of my Fucking house both of you. You make me sick"
With that said Mark grabbed his jacket and Addison got her handbag from the hallstand and they both left. As Derek paced around the house not knowing what to do, he noticed that some of Addison's CD"s were gone, he went into her study and noticed it was completely empty apart from the book case. He went back up to the bedroom and the scene of the crime and noticed all of her clothes and other personal belongings were gone.
She really was gone. Addison had planned on leaving him all along. What was he going to do now? Right now he was going to get drunk.
Mark and Addison left and drove back to Mark's apartment in silence. Even though they were now free to be together, being caught in the act was not the way they wanted Derek to find out about their betrayal.
How were they going to progress from this point?
A/N: Please tell me what you think. This chapter was a little difficult to write but I hope it came across as believable. Please review if helps to know what readers think. Constructive criticism is welcome.