In Charenton Asylum, the Marquis de Sade directs a play about Jean Paul Marat's death, using the patients as actors. Based on 'The Persecution and Assassination of Jean-Paul Marat as Performed by the Inmates of the Asylum of Charenton Under the Direction of the Marquis de Sade', a 1963 play by Peter Weiss.

The stern matriarch of a family that lives in a creepy mansion finds that a killer is hiding in the house, searching for a $600,000 fortune rumored to be hidden there and chopping off the heads of anyone who gets in the way.