It's 1910, and several strange deaths have occurred in the Central European village of Vandorf. When his father becomes one of the victims, Paul Heitz (Pasco) comes to investigate, and discovers that an old Greek legend resides in the area.
This film has the examples of:
- Agent Mulder: Prof. Jules Heitz, as evidenced by this exchange:Dr. Namaroff: We're the men of science. I don't believe in ghosts or even spirits nor I think you do either.
Prof. Heitz: That's one of the most unscientific remarks I have ever heard. I believe in existence of everything which human brain is unable to disprove.
- Comicbook Adaptation: A comic strip adaptation was made for the House of Hammer magazine.
- Get a Hold of Yourself, Man!: Prof. Meister slaps Paul when he is about to go look for Karla in distressed state.
- Downer Ending: On one hand the Gorgon monster Megaera has been taken down for good putting an end to this ancient horror's reign of terror. On the other hand however... that means that she takes Karla Hoffman with her and Paul dies shortly thereafter by being turned to stone and the last words of comfort that Prof. Heitz manages to speak to him that soften the blow are that this is the only way for her to finally be freed from the bond.
- Haunted Castle: Castle Borski, where Megaera turn her victims to stone.
- Leitmotif: Megaera's presence is made apparent with a One-Woman Wail.
- Locked into Strangeness: Paul's hair turns to grey after seeing Megaera from a reflection in water.
- Love Interest: Nurse Karla Hoffman for Paul.
- Medusa: The main villain.
- Novelization: Written by John Burke as a part of The Hammer Horror Film Omnibus.
- Off with His Head!: Megaera is decapitated with a sword in the climax.
- Opening Scroll: Gives the name of the setting for the horror to come.
- The Reveal: Carla is possessed by the spirit of Megaera, who takes her over every full moon.
- Sadly Mythtaken: The Gorgon is identifed as Megaera, one of the sisters of Medusa. The film takes liberties about the myth in this regard, since Medusa's sisters are actually called Stheno and Euryale in the Classical Mythology, and Megaera is the name of one of the three Furies.
- Taken for Granite: Megaera's victims turn to stone.
- This Was His True Form: When Megaera is killed, her decapitated head turns to Karla's.
- Town with a Dark Secret: The villagers of Vandorf live in fear of Megaera, covering up her misdeeds and try to drive away anyone who tries to investigate.