Private detective Drongo meets the incredibly beautiful Countess of Charleroi in Paris. He invites her to dinner, but the woman does not show up for the date. After some time, the detective learns that the countess was killed. The murder case is assigned to the experienced French investigator Anne Deschans, but an acquaintance from Interpol asks Drongo to help with the investigation. The detective carefully studies the countess's biography and comes to the conclusion that many people wanted her death: her husband, lover, former sponsor, servant - you can't count them all. But who is the killer? Drongo is ready to find the answer to this question at all costs...