Alberto Nardi is a Roman businessman who fancies himself a man of great capabilities, but whose factory teeters perennially on the brink of catastrophe. Alberto is married to a rich and successful businesswoman from Milan, Elvira Almiraghi who has a no-nonsense attitude and barely tolerates the attempts of her husband to keep his factory afloat with her money.

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.

Upon his return from battle in the previous film, the great warrior Hercules learns that his lover, Daianara, has lost her senses. Acording of the oracle Medea, Dianara's only hope is the Stone of Forgetfulness which lies deep in the realm of Hades. Hercules, with two companions, Theseus and Telemachus, embarks on a dangerous quest for the stone, while he is unaware that Dianara's guardian, King Lico, is the one responsible for her condition and plots to have the girl for himself as his bride upon her revival.