Brain surgeon, rock musician, adventurer Buckaroo Banzai is a modern renaissance man and has made scientific history. He perfected the Oscillation Overthruster, which allows him to travel through solid matter by using the eighth dimension. But when his sworn enemy Dr. Emilio Lizardo devises a plot to steal the device and bring an evil army back to destroy Earth, Buckaroo goes cranium to cranium with the madman in a battle that could spell doom for the universe. Along with his crime-fighting team, the Hong Kong Cavaliers, Buckaroo must stop the evil alien invaders from the eighth dimension who are planning to conquer our dimension. He is helped by Penny Pretty, the long-lost twin sister of his late wife, and some good extra-dimensional beings who look and talk like they are from Jamaica.