Author's note: A little warning: there is a mention of MerDer at the end of this chapter, only because I think it's important to explore Derek's side of this situation too, since I'm showing Mark and Addison's side, but I know most people who are reading this don't ship it, so don't worry, I do not plan on writing any more MerDer in this story.

This chapter is kinda long, I hope it's not confusing haha.

Anyway, I just broke my own heart writing this chapter lol.

Enjoy!

New York, 1989

All five of them are gathered at Addison's apartment, taking turns quizzing each other for exams.

Mark likes it that they're always helping each other. It's nice to know you can count on people when things get hard. They're friends. Even if he thinks they will probably be fighting over surgeries and patients in a few years. But he also thinks they will still root for each other, no matter what. They want each and every one of them to be happy, and they will do what they can to make that happen. That's what friends are supposed to do.

New York, 1991

She just delievered a baby, and he is so cute she can't stop staring at him, smiling.

She barely notices Derek's approach.

"Look at him", she points at the baby. "He almost died, but he is okay now. He's so beautiful ".

"He is", he agrees. He looks at her, curiously. "Do you think you ever want kids?"

"I don't know. Do you?"

He shrugs. "Maybe one day", he smiles.

"Yeah. Maybe one day", she smiles back.

New York, 2005

She was in love with Mark. Even before Derek left. It was not just sex, and she knows that now.

She shows up on his door late that night, carrying a suitcase, which makes her feel sort of stupid.

"Hey", Mark looks at her, then at the suitcase, then at her again, waiting for an explanation.

"I can't sleep in that house anymore", she says quickly. "Derek's presence is everywhere".

"Okay", he lets her come in.

She doesn't have to give further explanation, because he understands. She doesn't have to say that she wants to make things work with him so she won't feel like she threw her marriage away for nothing. She doesn't have to say that she needs him. She doesn't have to say anything before they kiss, urgently, their clothes off in a matter of seconds. He knows all of that. Most of the times they don't have to say anything to each other. They just know.

She wasn't sure before what exactly she felt for him. She banished any thoughts on that matter. She was married, she was confused, she was guilty and therefore she was scared of admitting any feelings towards him. But there is no reason to lie to herself now that Derek's gone. As she lies in bed with him that night, her head on his chest, his hand gently stroking her back until he stops and she figures he fell asleep, she looks at him and it hits her: she is in love with him. She is still scared to say it out loud. But maybe he knows that too.

Weeks pass and she feels like she's a teenager again. Being in some sort of forbidden relationship; people at the hospital looking at her and whispering to each other, judging her, pretending they weren't talking about her when she comes near them. It's like high school all over again. She wonders what kind of names they are calling her now.

Not that she cares anyway. She has too much to deal with right now; too many things she needs to figure out. There are moments when she is completely happy with Mark; that feeling you get when you finally find the thing that was missing for such a long time you had lost all hope of finding it. There are moments when she feels loved. There are moments when she stops worrying about everything because the two of them are the only thing that matters. But then there are moments when she's not sure if any of that is real, and she is scared. There are moments when she remembers what they did, what they're doing, and she is guilty. There are moments when that voice in her head insists that she shouldn't give up on Derek so easily.

"What's wrong?", he asks her one night after sex, noticing that she's upset.

"I just... feel terrible sometimes", she sighs. "I'm a cheater. I never thought I'd become a cheater".

"Well, there's a simple solution to that. Just ask Derek for a divorce", he says gently.

She shakes her head. "I can't do that. Not until I'm sure".

"I love you. Derek doesn't. What else do you need to be sure?", he sounds impatient now.

She takes a few seconds to process what he just said, surprised. He never said that he loved her before. Or at least not with words. She takes another few seconds to gather her thoughts. "I love you too. But I've loved Derek for almost twenty years. I can't just... I need more time to think".

"Fine", he says, but now he is upset too.

The truth is she has no clue what to do with her life anymore. She finds out Mark slept with someone else a few days later and it makes her even more uncertain. And apparently the universe thinks she doesn't have enough to deal with already; that's what she thinks when, a month later, her pregnancy test come out positive.

She sits on the bathroom floor, trying to calm herself down. She woke up earlier than him so she could take the test without him knowing about it, because she didn't want to tell him if she was pregnant. She had already decided to have an abortion if that was the case, so there was no reason to tell him that there ever was a baby. She can't have a baby now. They can't have a baby now. So she gets rid of the test and she doesn't tell him anything when he wakes up.

But her conscience won't let her have peace that day, or the next day. He deserves to know.

So the next day she waits nervously for him to wake up. She's trying to have some decent breakfast, but she can't eat anything right now. She takes a deep breath when he walks into the kitchen.

"Hey", he kisses her.

"Mark, we need to talk", she mumbles into his mouth.

"Right now?", he kisses her again.

"Mark", she breaks them apart. "We need to talk".

"Okay", his face turn serious, slightly worried. "What is it?"

She takes another deep breath. "I'm pregnant".

"What?", he is shocked. "Is it... are you sure it's mine?"

"Yes".

Then his shock turns into a smile and she's about to ask him if he heard it correctly. "We're having a baby?"

She frowns. "Are you... happy about it?"

"Of course", he is still smiling. "We're having a baby!"

She is shocked at first, and then the fact that he is happy makes her feel bad. She can't tell him about her abortion plans right now.

She avoids him at work because she doesn't want to talk about that anymore. But when she comes home at night and he's already there, she has to face it.

"Look what I got". He smiles and shows her a Yankees onesie and a calendar. "I marked the due date. I mean, it's just a guess, we still have to know for sure how long you've been pregnant-"

"Mark", she interrupts, softly. She just keeps looking at him and apparently her face says everything.

"You don't want this baby, do you?", he realizes.

"No", she admits, looking away.

"You want to have an abortion".

"Yes". She looks at him again. "I'm sorry".

"Because having a baby with me means that you'll never get a chance to go back to Derek", his voice is bitter now.

"It's not just that", she defends herself.

"What I don't understand is why", he continues, ignoring what she said. "Why would want to go back to him, why would you want to go back to being miserable when we could be happy".

She thinks about that for a moment, and then she shakes her head. "I can't just forget eleven years of marriage, Mark, I can't just wash eleven years out of my head. I wasn't always miserable with him. There was a time when he and I were happy".

And it was not just about Derek. The next day, when she catches Mark with a nurse, she is sure that this child deserves more than the two of them as parents. He says he loves her but he doesn't know how to compromise; she starts to think she's just another woman in his life, another woman he gets to screw. And she's in love with him but she still loves someone else. As she walks into the abortion clinic, she convinces herself that they would only ruin that child. As she walks out of the clinic and into her car, she breaks down. In another world where things wouldn't be so fucked up, that child would have a chance. She cries until she can't cry anymore and she realizes she never felt so alone in her life.

He was in love with Addison. Even before the whole affair thing began. He didn't know exactly when he had started to feel that way about her. Maybe months before. But she was still married to his best friend, and Mark is not someone who falls in love easily, so he banished those thoughts. Until the affair happened and he couldn't ignore it anymore, even though he still tried not to think about it because she was still married to his best friend and he wasn't sure if she felt the same or how she felt about him at all.

But that night she lies her head on his chest, something she never did before, and he immediately caresses her hair and her back, like it's the most natural thing in the world, and he can't repress any thoughts anymore. That's it. He is in love with her. And he thinks she might be in love with him as well.

He is in love with her and it scares him, because having feelings for someone is something that scares him, and the fact that he could lose her any minute because she still loves Derek scares him even more.

There are moments when he is absolutely happy with her, the kind of happiness you feel when you finally get something you've wanted for a long time but you couldn't have. There are moments when he is not scared because loving each other feels so good and it feels like it will be that way forever.

But then there are moments when she is clearly unsure about them and she is clearly thinking about Derek, never mentioning a divorce, and it's like you finally got that thing you wanted and now someone is threatening to take it away from you. And that's when he does the stupidest thing out of fear and anger: he sleeps with someone else, an attempt to prove to himself that she's not that important to him. That he doesn't love her that much.

When she tells him she's pregnant, he thinks maybe the universe is on their side this time. They finally have the chance to be happy together, to be a family. He has no idea how to be a father; his own parents neglected him for years and it wasn't until he met Derek, and the Shepherds would treat Mark like one of them, that he felt like he had a real family. But he's willing to try anyway. And then he discovers she doesn't think the same. So he does the stupid thing again, and she finds out this time, and he knows he just made everything worse.

She doesn't come home for the next few days, until she finally does, but she doesn't give him time to explain anything. "I need my stuff", she goes immediately to the bedroom, gathering her clothes and throwing them in the suitcase.

"Where are you going?"

"I've been called for a case in Seattle".

"You're going to Seattle?"

"Yes".

He finally asks the question that has been haunting him. "Did you abort our baby?"

"Yes".

He can tell she's hurt, even though she's trying to hide it. Even though she's assuming the "Satan" pose, trying to look cold and unaffected.

Of course she is hurt. He hurt her.

"Goodbye, Mark", she leaves the apartment.

He wanted to prove to himself that he didn't really love her that much. Except he does. And those last two words break his heart.

He fucked up twice. He fucked up with Derek and he fucked up with Addison. In two months he lost his best friend and the woman he loves. He asks himself when is he going to stop hurting everyone he cares about.

Seattle, 2005

He was in love with Meredith. He didn't plan for it. When he met her he was drowning himself in alcohol, trying to numb the pain of being betrayed by the two people in the world he trusted the most. But she wasn't revenge. He fell in love with her. And the two months he spent with her gave him hope. He could be happy again. He is happy with Meredith. The kind of happiness you feel when you've been in a toxic situation and then suddenly you're free. He could just forget that whole story. He could move on and never think about it again.

It seems like a good plan. Until Addison shows up in Seattle, and he is forced to face it.