A collector of esoterica, Dr. Maitland, buys an unusual skull from his ordinary source of artifacts. The skull is what remains of marquis De Sade. Much too soon he discovers how the skull affects him: by turning him into a frenzied killer.

Sir Matthew Phillips, seized by an unknown force, outbids his friend Professor Maitland at an auction for some items dealing with witchcraft. Marco, a dealer in the occult, visits Professor Maitland and offers him a biography of the Marquis de Sade. He also returns with a skull, allegedly de Sade's, stolen from the grave. Maitland refuses to buy it, even though Marco offers to sell it cheaply. That night, Maitland reads the book, has a nightmare, and awakens in Marco's apartment. He visits Sir Matthew, who is also interested in the occult, and learns that the skull was stolen from him; Sir Matthew warns Maitland not to touch the skull, relating how he had been seized by a spiritual force. Disregarding this advice, Maitland goes to Marco's apartment, finds Marco dead, and takes the skull. He becomes possessed by the skull and tries to kill his wife, but she is saved by her crucifix. Maitland dies in his own bedroom, his throat slit.