In ancient Rome, the people finally oust their despised king, Tarquinius, and declare the city a republic. Tarquinius makes an alliance with the Etruscan king, Porsenna, to take back power in Rome, but a Roman general, the heroic Mucius, sets out to stop him.
Maciste's village is attacked by pirates. The women, including Maciste's fiancee Guja, are carried off to Salmanak, where dwells the lair of the blood drinking Kobrak. Maciste vows to rescue them.
New inmate Rainbow has just been imprisoned for a year for his part in a fight over his girlfriend Wendy. After being assigned to kitchen duty, he becomes involved in a food-trading racket. When the scheme is betrayed to the prison's governor, its prime mover is threatened with an extended sentence...