The Humanoid: Hoping to overthrow his brother as ruler of the planet Metropolis, the evil Graal enlists the help of the insane Dr. Kraspin, who has invented a chemical capable of turning an ordinary person into a perfect soldier. They test this chemical on the pilot Golob, turning the unsuspecting victim into a mindless but indestructible automaton possessing superhuman strength. The people of Metropolis must somehow outwit Graal before he can create an army of these soldiers, or their planet will be destroyed.