Bobby Keller (Corey Feldman) and his best friend Dinger (Corey Haim) are carefree teens until Bobby gets knocked out one night and ends up in the body of an old man named Coleman Ettinger (Jason Robards) who is inside the head of Bobby. Ettinger has long believed he can transfer into the mind of a young person and regain his youth. Mrs. Gena Ettinger (Piper Laurie) seems to have a teenage husband now, and Lainie Diamond (Meredith Salenger) has an old man for a boyfriend, making for merry confusion as Ettinger starts to talk like a Valley Boy to his old friend (Harry Dean Stanton).