A furious light sabre duel is under way. DARTH VADER is backing LUKE SKYWALKER toward the end of the gantry.
A quick move by Vader, chops off LUKE's hand! It goes spinning off into the ventilation shaft.
LUKE looks round, but realizes there's nowhere to go but straight down.

DARTH VADER: "Obi Wan never told you what happened to your father."
LUKE: "He told me enough! He told me you killed him!"
DARTH VADER: "No! I am your father!"
LUKE: "No, that's not true! That's impossible."
DARTH VADER: "Search your feelings; you know it to be true."
LUKE: "NO!"
DARTH VADER: "Yes, it is true and you know what else? You know that queer brass droid of yours?"
LUKE: "Threepio?"
DARTH VADER: "Yes, Threepio, I built him when I was 7 years old."
LUKE: "No."
DARTH VADER: "Seven years old? And what have you done? Look at yourself, no hand, no job, and couldn't even levitate your own ship out of the swamp."
LUKE: "I destroyed your precious Death Star!"
DARTH VADER: "When you were 20! When I was 10, I single-handedly destroyed a Trade Federation Droid Control ship!"
LUKE: "Well, it's not my fault."
DARTH VADER: "Oh, here we go. 'Poor me, my father never gave me what I wanted for my birthday, boo hoo, my daddy's the Dark Lord of the Sith...waahhh wahhh!' You make me sick."
LUKE: "Shut up!"
DARTH VADER: "You're a slacker! By the time I was your age, I had exterminated the Jedi Knights!"
LUKE: "I used to race my T-16 through Beggar's Canyon!"
DARTH VADER: "Oh, for the love of God, 10 years old, winner of the Boonta Eve Open. Only human to ever fly a Pod Racer, right here baby!"

LUKE looks down the shaft. Takes a step toward it.

 DARTH VADER: "I was wrong. You're not my kid. I don't know whose you are, but you sure ain't mine. Get out of my sight, you loser!"

LUKE takes a step off the platform, hesitates, then plunges down the shaft. Darth Vader looks after him.

DARTH VADER: "And get a haircut!"