A/N: I don't own Grey's Anatomy! This story will not exactly follow episode plots but overall storylines. Zoe is introduced in the middle of Season 4.

It is Mark/OC, which will be slowly developed and will feature the OC's relationship with Derek as well as a friendship with Callie Torres.

Chapter One

She stood out.

She looked different than the other people at the hospital.

Most looked stricken. Or depressed. Or scared. A handful looked hopeful.

But this woman just stood out to Meredith Grey. She probably should be doing more than lounging at the Nursing Station and staring at strange women but it was a slow day and she was trying to avoid a certain neurosurgeon.

The woman just…looked like she was in awe. And there was a look of thrill in her eye that you usually didn't see in people not wearing scrubs.

And there was just something about that hair and jawline…

"That's not…" Mark Sloan trailed off. Meredith has never seen an expression like this on McSteamy's face before. There was no sly smirk in place, no flirtatious twist of the lips, no steely blue eyes. Just…disbelief.

"What? What's wrong?"

"That's Zoe Shepherd."

Meredith really hoped she wasn't another wife.

This was going to end badly. Mark just knew this was going to end badly. There was going to be carnage and bloodshed. The hospital would probably burn to the ground.

She had been gone for seven years. Seven years. And now she was in Seattle? In the same city as Derek.

God there was going to be bloodshed.

"Derek?" Zoe had found him. Two of the most violate Shepherds together once again.

Mark decided he should keep his distance to watch the show. His face was too pretty to get damaged. And his surgeon fingers too of course.

Derek's head turned. But no jaws dropped. And no gasps fell from any lips.

But his eyes went ice cold.

"Zoe?"

"Hey." A hesitant smile. Hesitance was not something Mark usually saw on the youngest Shepard.

"What are you doing here?" Disbelief colored Derek's voice. There was no sign of welcome, no happiness and no joy.

"I'm here to see you." Zoe announced quietly with a small smile.

A pause.

"But why?" Derek asked pointedly, his voice dripping with condescension and his tone growing more annoyed. "Why are you here?"

Zoe shook her head slightly. Not understanding.

"Are you here for money? What do you want Zoe?" Derek's voice grew louder and angrier. There was no more even and controlled tone.

Zoe looked as if Derek had slapped her in the face. And Mark felt uncomfortable and realized he shouldn't be here to witness this.

"You think that's why I came to see you? For money?" It was Zoe's turn to sound disgusted.

Derek laughed. But it was mirthless. "Why else? It's been 7 years."

"Exactly!" Zoe half-shouted. "It's been 7 years Derek. I missed you."

Derek turned away for a second. And then back again. "I can't deal with this right now. I have a surgery."

Derek walked away.

Zoe was left behind.

She looked different. But Mark guessed 7 years did that to a person.

She had the same expressive face. Angular and sharp but feminine.

A nose like Nancy's. Small and petite.

The bright green eyes. Squinted as usual.

Same dark hair. But shorter. It was never as pretty as the rest of her sisters. Always mussed, tangly and often altogether left ignored.

And Mark forgot how tall she was.

"So you're alive." He kept it simple.

Zoe hadn't noticed him until then. Her face didn't change at first as she took him in but then those tense lips spread into a smile and her eyes crinkled.

Mark couldn't remember Zoe smiling like that since she was a teenager. It was before John Barron came into her life anyway.

"Mark Sloan," Zoe greeted and then teased "still idolizing my brother?"

His smile was fast and genuine as if he couldn't stop it if he tried, "still pissing off your brother?"

Zoe's smile turned mischievous as she shrugged her shoulders and swayed a little bit, "Well we need some consistency in this chaotic world."

There was silence again. Their smiles disappeared. The two were unsure of what to really say to each other.

What did a guy say to his best friend's little sister after a seven-year disappearance act?

"Where you been?"

"Does it matter?"

"Not to me." He reassured quickly, "But it will to him."

She didn't have to ask what 'him' he was referring to.

"I was all over the place. I spent some time in Syria, then the Congo, I was in Africa for a while, then Peru, Cambodia, Afghanistan, and India." She exhaled.

"Doing what?"

She looked at him like he was an idiot. And Mark felt like the he was that dumb college boy being made fun of by the ever perfect knobby kneed and insufferably smartass teenage girl all over again.

"I'm a doctor, you idiot. What do you think?"

There was a pause.

"How long do you think it'll take for him to forgive me?"

"We should probably get a drink."

"Who was the girl?" Meredith asked as she began to scrub in next to Derek.

His eyes were unfocused as he stared into the Operating Room. His hands mindlessly repeating the motions he did so many times before.

"Derek." Meredith repeated. "Derek?"

"She was no one." He finally answered but he made no attempt to turn toward her.

"That's not true. I saw you yell at her."

"Oh you saw that?" He replied his tone cold.

Meredith was taken aback.

"She's my sister. And we're not talking about it."

"Oh so we have to talk about my mother and my family, but yours is off limits?"

If Derek heard her – and Meredith was sure he did – he ignored her and went on into the operating room.

They were at Joe's when he got a good look at her.

She was tanned. Deeply tanned. Long, tanned limbs that were gangly and malnourished. She was muscled as a teen from all of her sports, and toned as a 20 year old. But now, she was malnourished. She was far too skinny.

She didn't wear any make up so he could see the splattering of freckles over her cheeks. He missed the freckles. Zoe never bothered with makeup as a teenager, but when she met John…when she married John…she turned into a Beauty Queen. She turned into someone she wasn't.

Always heavy with the concealer and foundation. To cover the bruises. And John loved it when she wore red lipstick. Mark remembered an 18-year-old Zoe announcing it over Thanksgiving Dinner once.

Her mother spilled the red wine that Derek brought home from medical school all over the white tablecloth.

Zoe Shepard was just…so different.

"Last time I saw you you had showed up at Derek's and Addison's doorstep in your black widow glory."

She didn't react. But looked at him with that blazing look in her eyes. "And last time I saw you, Derek and Addison were happily married. Were you screwing her then or did that come later?"

'Still a viper' Mark thought. 'That didn't change'

"So you know about that?" Mark asked, feeling embarrassed.

"Yeah, I know about that." She said almost victoriously as she took a drink of her scotch.

"It wasn't-" Mark began to explain.

But she cut him off with a wave of her hand and an abrupt, "I'm not judging you."

Mark gave her an odd look.

"I'm not! I don't judge people outside of practice and the bedroom. It's a personal rule." Zoe explained cheerfully.

Mark just gave her an odder look.

The patient was dead within minutes of the surgery. Derek needed a drink.

Then he saw his baby sister perched at the bar next to Mark. Now he really needed a drink. But not here - not at Joe's.

"Derek!" He heard just as he slammed the door shut behind him.

He wasn't fast enough. Zoe was always the fast one. She was the athlete of the family.

"Listen, I don't want to get into it. I'm tired. And by the time I open my eyes, you'll probably be gone anyways." He was too tired for anger. Too tired to yell.

"I'm not going anywhere." Zoe apparently wasn't tired and she was ready for a fight.

"You say that now." And Derek wasn't too tired to be a condescending prick.

"I mean it." She said firmly. And then shrugged with a teasing grin, "I like the rain. I like the ferry boats."

Derek just chuckled darkly.

But Zoe wasn't giving up, "I'm staying Derek. I accepted the position as a trauma surgeon. I found an apartment. There's no foreseeable expiration date."

She paused. "I want to be your sister again. I want my brother back."

Derek walked away.

A/N: Thanks for reading! Please review!