La chambre ardente

Marc, his brother Stéphane, and wife Lucy spend their holidays at the castle of their old uncle Mathias, a descendant of the police officer who arrested the Marquise de Brinvilliers. She was a famous murderess who poisoned her victims, not to mention witch who laid a curse of violent death on all the officer's descendants. Mathias dies while all his guests are at a masked ball. The governess claims that, at the stroke of midnight, she saw a woman in old-fashioned clothes poison the old man.