A pair of smugglers manage to pick up a castaway while running from the authorities, who turns out to be the only survivor from a secret mission to destroy a mysterious superweapon designed by the evil Count Zartharn. The smugglers are soon recruited by the Emperor to complete the mission, as well as to rescue the Emperor's son, who has gone missing.
Hercules, a semi-divine being, squares off against King Minos, who is attempting to use science to gain power and take over the world. With the help of a benevolent sorceress, Circe, Hercules tries to save his beloved Cassiopeia from being sacrificed by Minos, and struggles against laser-breathing creatures and an evil sorceress.
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.
