Author's Notes:

Disclaimers: I don't own Grey's Anatomy (if I did, Derek would still be very much alive). Credit for the title goes to All Time Low.

This story is slightly different (ok, a little more than slightly different) than how Shonda's Grey's starts. You'll find many of the same faces carry a bit of a different story. You'll meet some new people, and I'll elaborate on characters we've only briefly seen.

I am and always have been, first and foremost, a Derek Shepherd fan. As we go forward, I think that will become very obvious. If I say anything more now, I'll give the story away, so I'm going to stop here.

Friendly reminder: You are reading ONE person's POV at any given time. There are always at least two parts to every story. Everyone has a story. Every character is this story is human. They make mistakes. They have flaws. No one is perfect. You will hear all of their stories in time. You just need to bare with me and give me time to tell them.

So, without further ado...

Old Scars, Future Hearts

Chapter One

We all have flaws.

We all make mistakes.

It's the bitter truth of being human.

Surgeon's don't like to admit they have flaws. We come at you with a scalpel and surgical drills- we are supposed to be perfect.

No matter the specialty- general, neuro, plastics, trauma, neonatal, cardio- your lives are in our hands when you're in our ORs.

Medical school is the easy part. Surviving intern year, residency, and fellowship are hard. Then, one day, you find yourself as an attending. You are the teacher now. You're on your own.

You are the one calling all the shots, all the medical decisions, and all the ethical decisions.

Ethics? Yea, they aren't my strong suit.

You see, I'm the jackass that slept with my best friend's wife and wrecked their marriage.

A 23 year friendship crumbled in less than 10 minutes. He hasn't spoken to me in almost 5 years. His ex-wife and I tried to make it work, tried to love each other to feel better about throwing away marriages and life long friendships.

We lasted a month and then she ran off with no explanation. I've always wondered why.

- Mark Sloan

"It's her birthday," the social worker said sadly. "What a birthday present."

Mark looked at him warily. He had just finished his last surgery of the day. He was tired of the hospital. He wanted to get to the nearest bar and find something to do for the night. He did not want some social worker he didn't know chatting his ear off at the nurses' station.

"I don't understand why her parents gave her up," he continued. "They are both richer than rich, they could have just hired a Nanny. Do you have any idea how hard it's going to be to get a practically inoperable brain tumor removed from a ward of the state?"

With a sigh, Mark turned to glance at the child in question. Even his cold heart could admit that finding an inoperable brain tumor in a four year old was a shitty birthday indeed. As he caught sight of her, his heart lurched.

He would know those eyes anywhere.

He hadn't seen them in almost five years. The last time he saw those eyes they were blazing with anger, hurt, betrayal, and all the other things a person feels when they catch their best friend in bed with their wife.

This little girl was a Shepherd.

Derek had wanted kids of his own since college. He had wanted kids with Addison, but she had been determined to put her career first. Mark knew that Derek had begun drifting away from her when he realized that Addison would never want the family he dreamed of.

There was not a chance that Derek Shepherd would willingly give up his child.

"How long would it take to get me cleared to foster her?" Mark asked quietly. "I'm a plastic surgeon, and I happen to have a best friend who they call the God of Neurosurgery."

The social worker's jaw dropped. "You'd be willing to take her?" he whispered. "Dr., I…"

"I have a three bedroom apartment, I can send a friend to make one of them a little girl's room," he said quickly. "There's a day care here she can stay in while I'm at work."

"I have to make a few phone calls," he said seriously. "This is as terrible as it sounds, but she's a huge burden in the eyes of the system. I don't foresee any issues. Thank you."

"Mark Sloan," he said extending his hand.

"Do you mind me asking what your income is?" the worker asked, turning red. "It's just…"

"I'm an attending plastic surgeon at a hospital on the upper east side," Mark said with a smirk. "My salary is enough to send her to college 20 times over. I make 4 million a year. Think that is good enough?"

The man's eyes bulged out of his head.

"This is my pager," Mark said, sliding a piece of paper towards him. "Page me when you get an answer. I'm going to track down a birthday cake."

"Wait!" the man called. "You mentioned knowing the God of Neurosurgery?"

Mark turned around, raising an eyebrow at the man. "I did. I take it you've heard of him?"

The man scoffed. "I've researched him, I was curious."

"Because you're dealing with a kid with brain cancer?" Mark asked, unease settling into the pit of his stomach.

"And because his name's on her birth certificate," the man spat.

"Quiet!" Mark hissed, pulling the man into the closest conference room and slamming the door shut behind him. "I figured that out the second I saw her, she's his clone. I have known Derek Shepherd since we were 5 years old, and I can promise you that he has no idea he has a child."

The man's eyes widened. "What?"

"Derek Shepherd has wanted kids since we were kids. Half the reason he divorced Addison was because he wanted a family and she didn't." Mark sighed, his anger at Addison growing by the minute.

"I'm Mike, Mike Gaston," he held out his hand for Mark to shake. "And I'm sorry to disappoint you, but Dr. Shepherd signed away his parental rights shortly after Abby was born."

Mark couldn't breathe. There was no way Derek would do that.

"I don't believe you," he said quietly. "He can't have known."

"Maybe he didn't want to stay married to Dr. Montgomery and felt a kid would get in the way. He is the one that filed for divorce, after all."

"He filed for divorce after finding me and Addison in his bed," Mark hissed. "I am telling you, Derek Shepherd does not know he has a child!"

Mike glared at the plastic surgeon as he pulled out Abby's file. He flipped through it quickly until he found what he was looking for- the form that said Shepherd didn't want the kid. With a smirk, he shoved it into Mark's hand.

"This proof enough for you?" he asked curtly.

Mark glanced at it, his eyes widening first with shock, then filling with anger.

Well, on the bright side, there was absolutely nothing stopping Derek from operating on her if needed. He would never think she was his, because just as Mark suspected, he didn't know he had a child.

"No," he snapped. "It's not. That is not his signature," Mark said coldly, shoving the paper back at the now shocked social worker.

"Do you think he would take her?" the man asked desperately. "If we could prove she's his and that he wants her, we could get someone to try. Wouldn't surgeons want to try for him, to try to impress him at least?"

"We aren't going to tell him anything until she no longer has a tumor in her brain," There was an edge to Mark's voice that caught the social worker off guard. "They don't call him the God of Neurosurgery for nothing- he can remove this tumor. He's my last resort because I'll be fired, but I have no doubt he can."

"I'm not sure whether you are doing this because you care about Abby or because her father is your best friend," Mike said softly, "but I have no doubt that you are the best option I have for her at the moment. I'm going to push custody through. I'll call you as soon as I can make it official. It shouldn't take long."

15 minutes later, Mark's pager went off.

"She's yours," Mike Gaston said gently when Mark called him back.

"I'll be in her room in 5," Mark said quickly. He turned to the intern assigned to him. "Shepherd, I need you to go buy me everything a four year girl's room would need. Have it shipped to my address, and take my card."

"A 4 year old girl?" Amelia raised an eyebrow at him. "Do you have a child you just found out about?"

"I'm fostering a 4 year old with brain cancer," Mark said softly. "So, if you can brainstorm ways to get your brother to answer my calls, that would be helpful too."

"Are you serious?" Amelia shouted chasing after him. "Since when do you foster kids?"

"Get out of here, Shepherd, or you'll be updating my charts for the next month."

Amelia was the little sister he never had. He'd been there through the death of Christopher Shepherd, through her descent into booze, boys, and drugs. He had been there through her stealing Derek's prescription pads and overdosing on oxycodone.

Liz Shepherd told him that Amelia had been living with Derek in Seattle while she was in medical school. It had done her a world of good, the entire Shepherd family could see that.

When she first got here, Amelia only spoke to him when absolutely necessary. Even then, it was one word answers with barely concealed anger. She clearly took Derek's side, not that he blamed her. He took Derek's side, and he was the ass that wrecked his marriage.

One word answers didn't cut it when she was on his service, however. He made that very clear. Amelia might be his baby sister, but he was her attending, and she would respect that. Over time, she softened towards him. He wouldn't say they were back to the relationship they had before he slept with Addison, but perhaps that wasn't possible.

After all, Amelia was a very different person now. She was happy. He hadn't seen her happy since the morning before her father was murdered in front of her.

They weren't as close as they once were, but she no longer hated him. Mark would even dare to say they had a budding friendship.

"There's no way Derek will speak to you!" she called.

Mark whirled around. "If he can't get the fuck over what I did to save a four year old's life, than your brother is the real jackass in this situation, isn't he?" he growled.

Amelia gaped at him. Who was this man, and what had he done with Mark Sloan?

She thought about it for a moment, her lips curving into a smile. Mark Sloan, foster father, were words that did not belong in the same sentence. Her smile fell a bit when what he said caught up to her. Brain cancer, foster kid; this had to be the same patient Dickens refused to waste resources on.

Amelia hated Dickens. After spending 4 years in Seattle with Derek, she could clearly see that the man was a medical dinosaur. He fit the neurosurgeon stereotype perfectly- he was arrogant, rude, and self-centered. He deserved to be taken down a peg. Mark was the perfect person for the job.

She glanced at the card Mark had shoved at her. His Black Amex. Sweet.

On her way out of the hospital to shop for Mark's new child, she grabbed her sister. No one could shop for kids like Lizzie. Besides, Derek wouldn't want to hear about Mark's change of heart and she needed to tell someone. Liz would do.

Once Mark told off his intern, he walked towards the girl's room. Abby, he reminded himself. The social worker told him her name was Abby.

He had absolutely no idea what to do with a child. He had played uncle to the sisters kids back when he and Derek were friends, but that had been years ago. What business did he have playing Dad to a four year old girl?

Mark hadn't seen the brain scans yet, but, clearly, the medical student hovering outside of Abby's room had. They didn't look good, he could tell by the look in the kid's eyes.

"Mark Sloan," he said quietly, extending a hand to the kid. "Abby's my new foster child."

"She's incredible," the student said hoarsely. "She's smart and funny, and she's four for fucks sake."

"Dickens is refusing to operate, isn't he?" Mark asked quietly.

Anger flared in the guy's eyes. "Dickwad says there is no point wasting the money or resources on a ward of the state."

Any thoughts he'd been having of telling Amelia the truth vanished. He was going to need Derek Shepherd, and in that case, no one could know what he had guessed. The knowledge that Abby was his daughter would be staying between him and Mike Gaston.

Mark looked at the boy critically for a moment.

"You were in the system, weren't you?"

The kid glared at him. "What's it matter?"

"Abby doesn't know she's getting a new home," His eyes widened. "I was hoping, since you already seem to be friends with her, that you would help me explain it to her. There will also be cake soon, I ordered one to be delivered."

He hated most foster parents on principle. They reminded him of his crappy childhood, so he sided with the kids and was a jerk to the parents.

The fact that this new foster father had earned himself the nickname 'McSteamy' didn't improve his perception of the man.

He mentioned a cake though, he thought. He's planning on celebrating her birthday, which already ranks him above almost every foster parent he's ever known.

"Why are you doing this?" he asked harshly. "What are you getting out of this?"

Mark deflated a bit. "You were in the system," he said quietly. "I'm not getting anything out of this. As to why I'm doing it, well I'm not that much of a heartless bastard. It's her 4th birthday, she's just been diagnosed with an inoperable brain tumor, and Dickens has his picture next to douche bag in the dictionary. I make four million dollars a year in plastics."

The kid was gaping at him now.

"I am a bachelor, and yes, I know it was your friends who christened me McSteamy. I have no use for that money. I'm hoping my name will get some decent neurosurgeons to consider operating."

"Dickens is an ass," he agreed, "but he is one of the better neurosurgeons in New York. If he's saying it's not worth trying…"

"If I can't get anyone willing to try," Mark took a deep breath, "then I will do whatever it takes to get Derek Shepherd here to do it."

"Alex Karev," he said, finally shaking Mark's hand.

Of course, Mark thought with a smirk. Mention having Derek Shepherd's number in your phonebook and suddenly everyone likes you. If you had told him that in high school, when Derek's afro was practically the size of a city block and he was the band geek, he would have laughed until he couldn't breathe.

Times sure have changed.

"Just to warn you," Alex said smiling softly, "She's quite the chatterbox."

Alex pushed the door open, and Mark quickly saw what he meant.

"AWEX!" the little girl shrieked. "They're winnin, Wex!"

"Are they?" Alex grinned broadly, sitting down beside her. "That's awesome, Abby!"

"That's Dewek Jeta!" she squealed, pointing at the television.

Abby Shepherd. Head full of black hair, looks just like Derek. Likes the Yankees.

Mark smiled as he added that observation to the very small list of things he knew about the girl.

"You like the Yankees?" Mark asked softly, sitting down in the chair next to Alex. "I'm Mark, I like the Yankees too."

Abby titled her head, her small brain trying to work out who he was.

Alex glanced at him questionably. Was he going to tell her or what?

"So, I have a question for you," Mark began, forcing himself to look her in the eye. "How would you like to live with me?"

Her eyes filled with hope. He didn't miss her pleading look towards Alex.

"Mark wants to be your foster Dad," Alex said gently, squeezing her hand.

"I have cancer," Abby said seriously.

"I know," Mark whispered, rubbing his hand up and down her leg in an attempt to comfort her.

"No one wants a sick kid," Abby parroted.

Alex had angry tears in his eyes. Mark could hear the hurt beneath those words. The fact that a 4 year old was experiencing that much hurt cut through him like a knife.

"I don't care that you have cancer now," Mark said quietly. "You might be sick right now, but you will not be sick forever. We're going to fight and you'll be at Yankee games in no time."

"Can I have a Dewek Jeta shirt?" she asked, her eyes wide with excitement. "And popakown?"

Mark smiled. "Of course you can."

"Is da cancer why my Mommy and Daddy weft me?"

"No," Mark said forcefully, ignoring the agony he was feeling. "It's not."

"So why?" she asked, pouting. "Did dey not lub me?"

Alex's grip on the side of the chair tightened.

"Your Mommy was scared," Mark whispered, forcing away his hatred towards Addison. "Your Daddy had to go to Seattle for work…"

"Where's Seattle?" Abby asked curiously.

"Far away," he chuckled. "It's 5 hours by plane. That's 1 and ½ Yankee games."

Abby's jaw dropped. "Wow, dat IS far!"

He nodded. "Your Mommy didn't think she could be a good Mommy. She wanted you to be with a family that loved you."

Alex snorted, earning a glare from Mark.

"And my Daddy?"

Mark took a deep breath. "Your Daddy doesn't know about you," he said gently. "Your Mommy never told him."

For just a second, Alex dreamed of bashing Sloan's face in. What the hell was he playing at?

Abby looked confused. Mark didn't blame her; just the thought of the mess Addison created gave him a headache.

"Why did he have to go to Seatley?" she asked.

"Because he's a doctor too," Mark explained.

Amelia froze in the doorway. She'd been listening for the past few minutes. Seattle. He's a doctor too. Your Mommy didn't tell him.

One look at the girl told Amelia everything.

As she stood there, listening to Mark defend a guy who hadn't spoken to him in 5 years, her respect for Mark Sloan grew exponentially. He didn't decide to foster a kid because he felt bad for her. He did it because she was Derek's.

"That's what I want," Abby piped up.

All 3 adults were confused.

"What?" Alex asked. "What do you mean, Abby?"

"I wanna meet my Daddy," she yawned. "No more cancer and meet my Daddy, dat's my birfday wish!"

Alex caught Amelia's eyes and his widened in shock.

Amelia Shepherd and Mark Sloan were practically siblings, the whole hospital knew that. From what he had heard, Sloan had been raised a Shepherd after befriending the brother at the age of 5.

He's a doctor too. Your Mommy didn't tell him. Seattle.

It was like a light bulb had gone off in his head.

Amelia came from a family of doctors. Most of the residents were constantly after her about her brother's fellowship. How common was the name Shepherd in medicine?

Then I will do whatever it takes to get Derek Shepherd here to do it.

Abby was Derek Shepherd's daughter. Holy crap.

Two weeks later, the three adults in Abby's life were exhausted.

Abby was tired too. Mark had dragged her to 4 different neurosurgeons in the past week. They all had the same answer.

It's too risky.

Surgery could kill her.

The last surgeon he consulted had left him seething.

"The only surgeon in the country that would even go near this mess is Derek Shepherd. He loses more patients than he saves- is that the man you want operating on this kid?"

"Considering if no one operates, she'll be dead in months?" Mark hissed. "That's exactly what I want, Dickens. Get Shepherd on the phone, ask his opinion."

"Sloan, the kid's a foster care hopeless case. Don't waste your time or money. Let social services give you another kid if you want to parent so badly. This kid will be a mess for the rest of her life if she survives, and quite frankly, I'm not willing to waste taxpayer money on that."

Karev had called just about every surgeon and oncologist in the Tri-State area. He was supposed to be moving to the West Coast within the week to start his internship, and he was spending every waking moment with Abby, Mark, and Amelia.

Mark wasn't sure how he was getting away with claiming Amy for his service when he wasn't operating, but he wasn't about to question it.

Amelia and Alex had confided their realizations in each other. Mark was still clueless that they knew Abby was Derek's.

Alex was afraid Mark would assume he was doing this to eventually have favors to call in with Shepherd, which ,although that had briefly crossed his mind, was not the reason he cared so much.

So, when Mark had tiredly informed them he had been calling Derek on and off for several days with no answer, he did his best to appear shocked.

"You think we've reached that point?" Alex asked dejectedly.

Mark's tear filled eyes answered that.

Amelia promised she would try to call him, but two days later, she didn't have good news either.

"He's ignoring my calls now too," Amelia said quietly as Mark exited Abby's room.

Mark cursed angrily. Derek was being a jackass and he didn't know what to do. Abby was running out of time.

"Karev!" he shouted at the former medical student. "Get over here."

"Is Abby okay?" he asked breathlessly.

Amelia smiled sadly. "She's the same as she was this morning."

"Say goodbye," Mark said softly. "We've got to get going or you'll miss your flight."

Mark had agreed to drive Alex to the airport. He had come to really like the kid. Karev was going to make one hell of a doctor. Even though Alex said he wanted plastics, Mark knew he would wind up in pediatrics eventually. He was too good with kids to play with boobs all day.

"Keep me posted," Alex begged as they pulled up to the airport. "Please."

"I will," he promised, his voice laced with sadness and pain. "Karev, you know if we can't find someone, we're looking at months."

"We'll find someone!" Alex shouted, tears filling his eyes. "She's 4, we have to find someone."

"I'm not giving up!" Mark assured the soon to be intern. "I won't ever give up on her, I'm just making sure you get the point we are at."

"You have to call me," Alex pleaded. "If something happens, if she turns worse…"

"I will call you," Mark promised. "And I will get you on the first flight out. Talk to your Chief of Surgery as soon as you can, let them know what's going on. I'm sure they'll be understanding."

Alex was unpacking his suitcase in the hotel room when he spotted pink.

He left New York on such short notice, he had no time to find a place to stay. Mark Sloan had given him money to crash at a hotel until he could get his bearings, which he greatly appreciated.

What the hell had Amelia packed in here?

Pulling it out, he bit back a gasp. How did she know?

Liz told me your internship is at Seattle Grace. I don't know if I want to hug you or punch you. He's not as intimidating as he seems, he just really dislikes Mark.

She had given him Abby's latest brain scans. His eyes widened and for the first time in several weeks, he felt real hope.

In the morning, he would start working at the same hospital as one of the best neurosurgeons in the country. The guy might be able to ignore phone calls, but he couldn't possibly be horrible enough to ignore an intern holding brain scans. Could he?

It was at the very end of a grueling first 36 hours that Alex finally found his target. Grabbing Abby's scans from his locker he walked towards the office with his stomach in knots.

This was her last hope. Mark knew it, Amelia knew it, and Alex knew it.

If Derek Shepherd said no, they would never find anyone willing to try. The mixture of hope and fear made Alex want to puke.

Well, here went nothing.

"Dr. Shepherd?" Alex knocked on the door.

Derek had just silenced another call from New York, this time from Liz. He had a very long day, and just wanted to get back to the trailer.

"Nelson's the on-call neurosurgeon," he said curtly. He was sick of these interns already.

Alex counted to 10. "I know, my shift's over too. I get it you've had a crappy day, I've had a crappy month. I just need your help for a minute."

That was a lie and they both knew it.

Derek eyed the envelope in the intern's hands warily. They didn't use those envelopes here, but they used them at Sinai. Who was this kid?

"Fine," Derek sighed, holding out a hand. "What am I looking at?"

He flinched when he saw the tumor. No one would touch something like that at Sinai. Hell, he could only name 3 surgeons who would even consider trying and he was one of them.

Damn it.

He was never going home tonight.