When his beloved Princess Deianira (Leonora Ruffo) goes mad, strong man Hercules (Reg Park) turns to the oracle Medea for advice. Medea tells him to travel to the underworld and find the Stone of Forgetfulness, a mysterious crystal that will cure Deianira's ills. Along with his friend Theseus, Hercules ventures into the dark and foggy depths of Hades to find the stone. Meanwhile, Deianira's power-hungry uncle, Lico (Christopher Lee), plots to steal the throne that is her birthright.
Director: Mario Bava and Franco Prosperi
Producer: Achille Piazzi
Cast: Reg Park, Christopher Lee, Leonora Ruffo, George Ardisson, Marisa Belli, Ida Galli, Franco Giacobini, Mino Doro and Rosalba Neri