Hercules (Steve Reeves) returns to Greece with his bride, Iole (Sylva Koscina), and their young companion, Ulysses (Gabriele Antonini), after a number of perilous escapades at sea. The three are immediately beset by a series of trials, each more difficult than the last, and also learn that the kingdom is on the verge of collapsing into civil war. Hercules must defeat his enemies and unite the people while resisting the magical allure of the beautiful Queen Omphale (Sylvia Lopez).