Journalist Claude Leroy (Jacques Champreux) reports that a secret society, The Companions of Baal, is behind a hold-up in the small town of Blaingirey. They are led by the Grand Maître Hubert de Mauvouloir (Jean Martin). An adorant of Lucifer, he aims to enslave the world. Accompanied by their acolyte, Pierrot Robichat (Gérard Zimmermann), and a young girl, Françoise Cordier (Claire Nadeau), Claude Leroy is determined to finally reveal the mysteries of the group's criminal enterprise.