Divisional Inspector Bricot sends two detectives to the French Riviera to dismantle a drug deal in a carnival mask factory. However, knowing the low efficiency of his subordinates' work, he goes down to Nice to conduct the investigation.
In a moment of madness a respectable pharmacist kills a young woman who is sun-bathing by a lake. When the murdered woman's boyfriend is falsely accused of her murder, the murderer is chosen to serve on the jury. Based on Francis Didelot's novel "Le Septième Juré".
In a moment of madness a middle-aged, married and respectable pharmacist kills a young woman who is sun-bathing by a lake. Unable to take in what he has done, he flees from the scene of the crime and behaves as if nothing has happened. Eventually her boyfriend is charged with the crime and, in a strange twist of fate, the killer finds himself serving on the jury.