Based on the Edward Bulwer-Lytton novel. Set in the shadows of Mt. Vesuvius just before its famous eruption, the film begins with Glaucus, a Roman legionnaire, returning to his home from far-off wars. Upon arriving, however, he discovers that his father has been murdered by a gang of black-hooded looting bandits. Glaucus vows revenge against the killers, but just how high up are those involved?

En route to Thebes for an important diplomatic mission, Hercules drinks from a magic spring and loses his memory. He spends most of the movie in the pleasure gardens of Queen Omphale of Lydia. While young Ulysses tries to help him regain his memory, political tensions escalate in Thebes, and Hercules' new wife Iole finds herself in mortal danger.

In this melange of characters and events from separate mythological stories, Hercules, demigod and superman, arrives in the ancient Greek kingdom of Iolcus to tutor Iphitus, son of king Pelias; immediately on arrival, he falls in love with the king's delectable, briefly clad daughter Iole. Before he can win her, he must succeed in a series of quests, in the course of which he teams up with Jason, true heir of Iolcus, whom he accompanies on the famous voyage of the Argonauts.