Gerald (Edward de Souza) and Marianne Harcourt (Jennifer Daniel), are a honeymooning couple in early 20th-century Bavaria who become caught up in a vampire cult led by Dr. Ravna (Noel Willman) and his two children Carl (Barry Warren) and Sabena (Jacquie Wallis). The cult abducts Marianne, and contrives to make it appear that Harcourt was travelling alone and that his wife never existed. Harcourt gets help from hard-drinking savant Professor Zimmer (Clifford Evans (actor)), who lost his daughter to the cult and who finally destroys the vampires through an arcane ritual that releases a swarm of bats from Hell.