Historian Michel Boissard, is invited with his wife Marie, a descendant of the Marchioness of Brinvilliers, the notorious poisoner, to the château of Mathias Desgrez. Mathias Desgrez is a descendant of the last lover of the Marchioness, who denounced her. Mathias is adept in the occult arts, which he practises with his friend Dr. Hermann. To the château come Marc Desgrez, and Stephane Desgrez, nephews of Mathias, who are waiting impatiently for their inheritance ...
