The year is 1978: 12-year-old Joey Cramer, playing in the woods near his home, is knocked unconscious. He awakens and heads home, only to find strangers living there.
He also finds that the year is 1986, and that he's been officially missing for eight years. NASA officials determine that Cramer was abducted by aliens during his blackout, and hope to scan the boy's brain in order to unlock a few secrets of the universe.
Answering the call of a strange, unseen force, Cramer boards a well-hidden spaceship and takes off, guided by the jocular voice of a computer named MAX (voiced by none other than Paul Reubens, aka Pee-wee Herman).
Realizing that he can't fit into 1986 so long as he's a child of the seventies, Cramer hopes to retrace the steps of his alien abductors and get back to his own time.