Troubled, Marty decides to go to Doc's lab after school by himself once he drops Jennifer off at her house. He knows Doc is still probably absent, but Marty longs for his advice and guidance that has always been so helpful to him. Marty parks his truck in the alleyway and walks up to the door. He reaches underneath the doormat, but to his surprise, the key that is normally there is now gone. He lifts up the entire doormat but there is nothing. He stands back up and tries the door and it is unlocked. He steps in to see that the lights are on and he is astonished. There is Joan.
Marty: Joan! What are you doing here?!
Marty catches on to what Joan is trying to do. He sees Joan with her guitar strapped to her body. She has it plugged into Doc's giant wall-size amplifier. Joan gasps after Marty speaks and she immediately turns around in her white Ramones t-shirt, loosened black-striped tie, ripped blue jeans, and oversized black aviators.
Marty: Don't you know whose place this is?
Joan: Uh, yeah, the wackjob who's always in the local newspaper! Wait, how did you know I was here?
Marty: I didn't, I... uhh... I know Doc. Just wanted to stop by and clear my mind.
Joan: You know him? Dr. Brown hasn't been in the newspaper recently so I wanted to see if he was okay. Oh, Marty, please don't tell anyone, okay? Don't tell him! I swear I was just gonna try the amplifier and then leave. I saw it through the window.
Marty: Don't worry about it. But, uh—.
Joan: Do you know where he's been?
Marty: Uh, no, I just... I haven't seen him since maybe about a month ago. But wait, I wouldn't—.
Joan: Come on over here, let's try it out!
Marty: Hey! I wouldn't do that! Seriously.
Joan: Why not?
Marty: Uh, well [puts hand on the back of his neck], I tried that before and it overloaded and broke... uh, exploded... uh, Doc must've rebuilt it but he was pretty angry.
Joan: Oh, come on, I came all this way. If he rebuilt it, we will test it again.
Marty: No [extends arm and holds hand out to stop Joan]! It's still experimental, it will break.
Joan: Come on, Marty.
Marty: Joan. Please.
Joan: I need to keep rockin'.
Marty: Joan! Please don't do it! For me!
Joan: And I'm never gonna stop!
Marty: Joan!
Joan: GOTTA KEEP ON ROCKIN'!
Marty: JOAN!
Joan: Hmph. Fine. I'll just leave now. I wasn't gonna do it.
Joan turns off the amplifier and unplugs her guitar. She then takes out her blue pick, brings it up to eye level, and strums her guitar with one hard sweep. Marty flinches before he notices she first unplugged her guitar.
Joan: [chuckles] Ha! Gotcha there!
She stores the guitar in its case, puts her aviators in her hair, and walks towards the door where Marty is standing. Marty feels chills down his spine, his fear of Joan's presence amplified after the incident at lunch that day. Marty's heart races and he cannot muster the strength to apologize to Joan. He stares at her dead in the eyes as she walks closer to him but her intimidating presence only makes him want to hide in a corner. Too late. Joan is already beside him and she speaks.
Joan: That's a nice little car he's got over there [points behind herself with her thumb to a simple homemade model car on a table]. What do you think? Trans Am?
Marty: Uh, no, I think that's a... a DeLorean, maybe.
Joan: No way! They got one of those at the Buick dealer down the street... Hey, you ain't gonna tell, right?
Marty: You don't trust me?
Marty kicks himself, for he realizes that is the worst thing to say to Joan at that moment after her knowing all the bad things he said about her. There is no way Joan still trusts him.
Joan: [chuckles] If you tell, you know what's gonna happen [uses arm to pretend to punch Marty]?
Marty: [flinches] I won't tell. Just, please don't break any of his stuff, that's all.
Joan opens the door and walks outside. She forgets something and turns back to Marty.
Joan: I hope you won't. Thanks a bunch. Oh, I forgot the key [reaches into her jeans pocket and tosses the key to Marty]. I won't be back here, then. You can hide it somewhere else besides the doormat if you don't believe me.