The body of a dead woman is found in a barrel hurtling down a hill in the middle of the night. The prime suspect is the husband, a violent and jealous painter from Collioure, for whom the victim was both model and muse.
A man is found hanged in a tower in La Rochelle. A letter A for avarice is drawn on his forehead, a method used in the 17th century to punish those committing a Deadly Sin. Raphaël Weiss investigates on the orders of Justine, his daughter.
While working on the Palais des Papes workers discover a 14th century secret chamber. Inside is a woman's skeleton. The autopsy shows that the victim is a childhood friend of the investigator handling the case. A second body is soon found.
In Saint-Martin-de-Ré, a dead man is discovered, wearing prison clothing. Assigned the delicate case, Vincent Pelletier also has his half-sister looking to reopen the case of their father, imprisoned in Saint-Martin.