Alterations by Kristina Feedback is most appreciated!

Disclaimer: I don't own "Back to the Future" in any way shape or form. No copyright infringement intended, no money made.

When he comes back from the tracks the shock has dissipated enough for him to sit down and make a list of all the things that are different.

Some changes are obvious. His mother smells of perfume instead of whiskey and slips a pack of condoms in his pocket when she thinks he's not looking. His father looks like he's spent five thousand dollars on a face lift. His sister, who he remembers as an unhappy virgin, seems to be neither in this reality.

Others are less tangible and also creepier. These are the changes made to the common wealth of memories he no longer shares with his family.

He has spent the last two days figuring things out by looking through photo albums and starting conversations with, "Hey, remember when…"

He writes down key events in the list of things to compare. One column for the events that match up. Setting the rug on fire – check. Getting drunk at Camp Tahome – check. Meeting Jenn by falling on his ass in front of her – sadly, check.

He makes another column for the events that don't match up. Lorraine not being thrown out of the PTA for being drunk. Dave actually having the guts to apply for a managing position after working the grill for two months. The dog dying of cancer and not from Biff running it over. The trip to Grand Canyon. Uncle Joey's parole party (the support of his loving family had gone a long way apparently.) All anecdotes from a happy childhood that everyone seems to remember but him. He wishes now he had remembered to ask Doc how they met, but being busy saving the world it had somehow slipped his mind.

Sunday night, a very tall woman in artfully ripped jeans is having coffee with Lorraine in the kitchen. He doesn't remember seeing her before and figures she must be an acquaintance from the new timeline, although acquaintances don't tackle you when you say hello. The woman jabs him in the ribs until his eyes water and Lorraine is saying, "Now Marty, you promised not to nag your sister."

Many years from this moment, Marlene will be sick with the mumps and he will be watching a re-run of Buffy the Vampire Slayer, the episode where she suddenly has a fake sister, and he will feel himself go numb.

He'll figure, between the two of them, Buffy got the sweeter deal. At least those weird monk types had the good taste to implant fourteen years worth of memories in her. They were fake memories, of course, but at least she didn't have to pretend to be familiar with a total stranger.

But sadly, no such luck for him. Seventeen years of having another sister are lost somewhere down the drain along with the memories of a strong father and caring mother.

He writes "Number of siblings" in the column of things that don't match up.

He racks his brain trying to remember what he did. He knew that screwing with the past fundamentally changed his family, but he could never have imagined that those changes would involve actually creating a person.

The only conclusion he can come to is that boosting his father's confidence had sped things up a little. Maybe his parents even fooled around once they left the dance, and oh man does he not want to think about that.

Before the evening is over he's got the basics down. The mystery sister is twenty-nine and an assistant at a record company in San Francisco. Her name's Leanne, and he has the sneaking suspicion she's brought him to watch a concert or two.

She must be the first McFly to ever leave Hill Valley. Marty wishes he could leave too. Having seen his future, he's not so sure he will.

He was never at the top of his class, but even he can do the math. Twenty-nine, yeah, they must have done it straight away.

And sure enough, the wedding pictures are different. Gone are the photographs of the sombre Presbyterian nuptials in ´62 where his father looked old and his mother as if she was facing her execution. Instead, they portray a version of his parents who look about the same age as when he left them at the dance. Lorraine is cute in her off-white petticoat. George is practically beaming. He recognizes the inside of the old courthouse. It seems fitting, somehow.

When he casually mentions it to Linda, she giggles and talks about a shotgun wedding.

"It's romantic though, isn't it? I mean, he could have just bailed out, like some guys would, but he proposed to her, and they made it work, you know. Because he loved her. They knew they were destined for each other. They just knew."

Yes, Marty thinks grimly, they knew because of me.

If only he had someone to talk to.

He's told Jenn the basic differences between the timelines, but she adores Leanne and he wouldn't want to ruin her illusion. More than anything, he wishes Doc was here.

He acts as normal as he can around his family, trying not to mind the fact that there are now three graduation pictures in the dining room. He tries to keep up with the bantering and the mandatory game of Monopoly, but it doesn't feel natural no matter how hard he pretends that it does.

Leanne follows him into the kitchen. "I know why you're acting funny."

He nearly chokes on his Pepsi. "You do?"

"Yeah, uh… I'm sorry, Marty, but it just wouldn't seem right for me to push something like that on my supervisor." She shifts uncomfortably. "You know, with you being my brother. It would be better if you went through regular channels. It's a really good demo, though," she adds, almost as an afterthought.

He nods and thinks; funny, you wouldn't be alive if it wasn't for me.

Monday night they sit down for a family meal. Leanne's going back tomorrow morning, and Lorraine's showing off her culinary skills. In the middle of Dave's lengthy account of his re-organization at work, the door bell rings.

"I'll go, mom."

"Leanne, no." Lorraine shakes her head frantically at her husband. "George…"

But Leanne is already up, opening the door to reveal a cowering Biff Tannen who is tall enough for her to see him eye-to-eye. "Can I help you?"

Biff opens his mouth but he is cut off by George appearing suddenly in the door frame. "You got the reports done?"

"Oh, Mr. McFly," Biff's face light up in a yellow-toothed grin. "I sure did." He hands a manila envelope to George who takes it with a disinterested look. This new, weak-minded Biff takes a lot getting used to, and Marty can't help but wonder why his father has kept him around all these years.

George doesn't seem impressed. "Can I also assume that you fished out the drain pipes and that you plan on redoing that third rate paint job you did for me last week?"

For the flash of an instant Marty thinks he can see the old Biff reappear like a dog sticking its head out to size up its opponent, but then the ingratiating smile is back on and Biff seems to shrink before his eyes.

"First thing in the morning, Mr. McFly."

His nervous chattering dies down as his eyes fall on the dinner table. From his seat Marty can see that his eyes are gleaming. "Sure must be nice having the whole family together for the holidays."

"Yes, it is." George says thoughtfully. "It gives you a chance to really appreciate how lucky you are. Lorraine and I are very happy."

Biff blinks, and for a moment it seems as if he had lost his tongue. He turns to Leanne and Marty could swear that his father is clenching his fist. "How about you, Ms. McFly? Are you home for Halloween?"

"I think you should leave now," George says coolly.

"Wow, dad, you didn't have to be that cruel to him," Linda says later, as the door is slammed and Lorraine is breathing normally again.

"Yes," George says firmly. "I have to be."

For many years Marty will be able to recall the instant of terrifying clarity when he sees his mother's ghastly face and his father's whitened grip on Leanne's shoulder.

To his defence, he will say that he only ever meant well. He will tell himself that he was thrust into a responsibility he had no way of preparing for, and that all he did was try to put things right again. Telling himself these things will make it easier to sleep, and he'll repeat them over the years until the lines between truth and reassurance are blurred and he forgets how he could ever have believed otherwise.

But it never changes the fact that through his tampering with the universe he got his father murdered once and his mother raped.

If only he could go back.

But he can't, and he wouldn't if he could, because you can't murder your own sister. Their lives are better now, anyway.

He goes on treating his family with the same kind of bantering affection that he always dreamed of doing, until he gets so used to the changes that he hardly ever thinks about the fact that they used to be different.

He watches his father torment Biff and stops wondering why his parents never told on him. Lorraine would never risk her daughter finding out, and there are different kinds of punishment.

He tries to look at Leanne like an older version of Linda, and after a couple of years it's easy to pretend he always had two sisters.

If he would ever ask her, she could tell him about growing up coddled and spoiled, of being pampered and over-protected by their parents. It was almost as if the gifts and the constant affirmations were a compensation for something. She doesn't know for what.

But he doesn't ask, and though they stay close over the years through the births of their kids and the deaths of their parents, she sometimes catches him staring at her with an odd look in his eye.

It's absurd, but she could swear it looks like pity.