Marty: We do now.
Cut to Doc examining the flyer. He's walking around, thinking as he talks.
Doc: This is it. This is the answer. It says here that a bolt of lightning is gonna strike the clocktower precisely at 10.04pm next Saturday night. If we could somehow harness this bolt of lightning, channel it into the flux capacitor, it just might work. Next Saturday night, we're sending you back to the future.
Marty: OK, All right, Saturday is good, Saturday's good, I could spend a week in 1955. I could hang out, you could show me around.
Doc: Marty, that's completely out of the question, you must not leave this house. You must not see anybody or talk to anybody. Anything you do could have serious replications on future events. Do you understand?
Marty: Yeah, sure, OK.
Doc: Marty, have you interacted with anybody else today, besides me?
Marty: (mumbling a bit) Um, yeah, well I might have sort of ran into my parents.
Doc: Great Scott! (realises something) Let me see that photograph again of your brother. Just as I thought, this proves my theory, look at your brother.
Now Marty notices that Dave's head is vanishing.
Marty: His head's gone, it's like it's been erased.
Doc: Erased from existence.
Hill Valley High School. Doc and Marty walk up to the entrance and go inside. Marty is amazed.
Marty: Whoa, they really cleaned this place up, looks brand new.
Doc: Now remember, according to my theory you interfered with your parents' first meeting. They don't meet, they don't fall in love, they won't get married and they won't have kids. That's why your older brother's disappeared from that photograph. Your sister will follow and unless you repair the damages, you will be next.
Marty: This sounds pretty heavy.
Doc: Weight has nothing to do with it.
Inside the school, Doc and Marty see students walking to lessons. George is one of them. Some boys are behind him.
Doc: Which one's your pop?
Marty: That's him.
Marty points at George, and we cut to see him. The bullies have pinned a Kick me sign on his back, and are doing just that.
George: OK, OK you guys, oh ha, ha, ha, very funny. Hey, you guys are being real mature.
Cut back to Doc.
Doc: Maybe you were adopted.
Cut back to George.
George: OK, real mature guys. OK, Biff, will you pick up my books?
He doesn't do so because MR STRICKLAND arrives. He's still bald, even in 1955!
Strickland: McFly!
Cut to Marty.
Marty: That's Strickland. Jesus, didn't that guy ever have hair?
Cut back to George and Strickland.
Strickland: Shape up, man. You're a slacker. You wanna be a slacker for the rest of your life?
George: No.
Cut back to Marty and Doc.
Doc: What did your mother ever see in that kid?
Marty: I don't know, Doc, I guess she felt sorry for him cause her dad hit him with the car... hit me with the car.
Doc: That's a Florence Nightingale effect. It happens in hospitals when nurses fall in love with their patients. Go to it, kid.
Marty walks over to George - Strickland has now gone.
Marty: Hey George, buddy, hey, I've been looking all over for you. You remember me, the guy who saved your life the other day?
George: Yeah.
Marty: Good, there's somebody I'd like you to meet.
Marty spots Lorraine and her friends and leads George over to them.
Marty: Lorraine.
Lorraine: Calvin!
Marty: I'd like you to meet my good friend George McFly.
George: (shyly) Hi, it's really a pleasure to meet you.
Lorraine: (ignoring George, to Marty) How's your head?
Marty: Well uh, good, fine.
Lorraine: Oh, I've been so worried about you ever since you ran off the other night. Are you OK?