The series tells the story of a serial killer dubbed “The Monster of Florence” by the Italian media, who terrorized the province of Florence from the late 1960s to the mid-1980s. He committed eight double murders, typically targeting young couples and always using the same weapon — a Beretta 70 pistol. The true identity of the killer was never determined, and the investigation was reopened several times. The series explores the stories of several possible suspects.