On the eve of his promotion, Rome's chief homicide investigator, the Inspector (Gian Maria Volonté), goes to his mistress Augusta's (Florinda Bolkan) apartment and calmly slits her throat. Littering the crime scene with fingerprints, footprints, and dozens of clues, he plans to show the world just how powerful he really is, a man above suspicion. With the Inspector's help, his successor eventually makes an arrest. Despite every clue pointing to the Inspector, Augusta's downstairs' neighbor, a young student, is accused of the murder. Paranoid and completely exhausted, the Inspector, whose associates have refused to believe the obvious, finally confesses to the crime.