A newly acquired obsidian mirror in the Tuileries Palace reflects not the viewer but a grotesque, distorted version of their soul. Soon, members of the court begin succumbing to madness and committing unspeakable acts, seemingly possessed by the reflected entities. Dupin is summoned by a desperate King Charles X to investigate the mirror's origins, uncovering a history of dark magic, forbidden rituals, and a haunting tale of a queen consumed by vanity and summoned a demonic force.