While a young woman is found dead in the back seat of a car, the inspector in charge of the case discovers a casino chip stuck between the fingers of the victim. Intrigued by this unusual track, he goes back to a secret game circle with rather sulphurous rules. Indeed, the customers are each time ruined by the croupier, and are calmed by the hostesses present in the establishment, who do not hesitate to drug them to take advantage of them. The policeman decides to immerse himself in the particular atmosphere of this game circle, in order to lead the investigation but also to enjoy the pleasures that can be offered to him ...