Simon Cordier is a well-respected magistrate who visits a condemned prisoner, Louis Girot, just before the man's execution. Girot again pleads his innocence insisting that he has been taken over by a spirit that forced him to commit his crimes. Cordier doesn't believe him and the man suddenly dies. Cordier does however note a rapid change in his personality during their short interview. In the following days, Cordier must face a number of strange occurrences in his home. He begins to wonder if he is sleepwalking but is soon hearing voices and begins to wonder about his sanity. It's recommended to him that he take up sculpting, something he once had an interest in. He develops a relationship with Odette, a gold digger married to a struggling artist, but the evil, invisible spirit soon drives him to murder.

Jason has been prophesied to take the throne of Thessaly. When he saves Pelias from drowning, but does not recognize him as the man who had earlier killed his father, Pelias tells Jason to travel to Colchis to find the Golden Fleece. Jason follows his advice and assembles a sailing crew of the finest men in Greece, including Hercules. They are under the protection of Hera, queen of the gods. Their voyage is replete with battles against harpies, a giant bronze Talos, a hydra, and an animated skeleton army, all brought to life by the special effects wizardry of Ray Harryhausen.

Architect Larry Coe has a wife and family, but becomes embroiled in an affair with beautiful Maggie Gault...