Nounours is the alias of a "relative" informant who has a special deal with the police: he receives 10% of the drugs collected as a reward for his assistance. Inspector Gérard Delvaux assumes command following the suicide of his personal contact, inspector Maurin. In the meantime, Judge Lambert is revealing the unlawful conduct of the police officers. Her tenacious investigations, which had caught Maurin, are now pointing to Gérard and Nounours as the source of the heroin that caused recent fatal overdoses. Nounours promises Gérard ever larger catches, which he is determined to realize before he is compelled to divulge who Nounours is to Lambert's judgment.