In this live-action adaptation of the Hank Ketchum comic strip, the half-pint hooligan (Mason Gamble) unintentionally frustrates Mr. Wilson (Walter Matthau) to the point of catastrophe, though the good-hearted Mrs. Wilson (Joan Plowright) agrees to baby-sit while Dennis' parents are away. After several disasters, Dennis runs away, right into the arms of crook Switchblade Sam (Christopher Lloyd).