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.

A petty thief pretends he is Mussolini's personal physician, wins the confidence of a family, and succeeds in stealing their gold cutlery.

Red and Carraucho, after escaping from jail, reach the border to Mexico and are hired by Morgan, a rich silvermine owner. Disgusted by the latter's cruelty, especially against the local peones, the two support a revolt organized with the aid of Mrs. Vivian, wife of the ruthless tyrant.

A young French girl, Yvonne, having won a competition, goes to Capri for a short break. There she meets Baron Vanvutelli, an old-fashioned old man, Mario, a Roman student, who came to spend the Sunday at Capri, along with two friends, Renato and Julius.