D'Eon de Beaumont discovers that his older sister, Lia de Beaumont, has been murdered. Determined to solve the mystery behind her death, he joins the French secret police in their investigations of the disappearances of a number of young women. After D'Eon reveals a secret document to his friend, Bernis, the members of the secret police are murdered and Bernis is abducted. D'Eon is asked to surrender the document in exchange for Bernis's life, but when he makes his way to the rendezvous point, he discovers that Bernis has been transformed into a zombie-like creature.