It's 10.03pm. The Marty from the first film (called 1955 Marty here) is about to get sent back to the future. Cut to Doc at the clocktower. He's on it holding the cables. He watches the DeLorean from the first movie approach the clocktower. Doc finishes connecting everything and then slides down the rope.

Doc: Argh!

Cut to 1955 Marty in the DeLorean. The DeLorean hits 88mph and lets off blue flashes - it's about ready to travel through time.

1955 Marty: Doc!

Cut to Doc. Doc gets the cable out of the branch. The clock turns to 10.04. Lightning strikes it, and the lightning causes electricity to go down the cables, which Doc reconnects just in time, getting himself a slight electric shock as he does so.

Doc: Ahh!

The lightning enters the flux capacitor. 1955 Marty gets sent back to 1985. Doc dances with delight because the experiment was successful.

Doc: Yoo! Ha, ha, ha!

And then he turns to the Courthouse. After looking at it, he turns to his car - and 1985 Marty (the one we've been following through Part 2) comes running up to him.

Marty: Doc! Doc! Doc!

Doc: What?

Marty: Doc!

Doc turns and sees Marty.

Doc: Argh! A ghost!

Marty: OK, relax Doc, it's me, it's me, it's Marty!

Doc: No it can't be you...I just sent you back to the future!

Marty: I know, you did send me back to the future, but I'm back, I'm back from the future!

Doc: Great Scott!

He faints, and Marty bends down to tend to him.

Marty: Doc. C'mon.

CREDITS FOR PART 3.

Marty drives Doc home, back to Doc's mansion. He gets the still unconscious Doc out of the car and takes him inside.