An alien takes the form of a young Wisconsin widow's husband and makes her drive him to his departure point in Arizona. Distrustful government agents, along with a more ambivalent scientist, give pursuit in hopes of intercepting them.
Adventurer, brain surgeon, rock musician Buckaroo Banzai and his crime-fighting team, the Hong Kong Cavaliers, must stop evil alien invaders from the eighth dimension who are planning to conquer Earth.