On the morning after the celebration of the famous crime novelist Harlan Trombi's 85th birthday, the guest of honor is found dead. It is an obvious suicide, but the police, following protocol, question all the family members present in the mansion, although the matter is of greater interest to private detective Benoit Blan. That same morning he receives an envelope containing cash from an unknown sender—a request to investigate Harlan's death. It doesn't take an experienced investigator to see that everyone is embellishing their relationships with the late head of the family, but Blan gets a real gift—the nurse of the deceased, who cannot bear lies.