This movie starts with three men arrested for disorderly conduct at a dance. After they are released, they take a train trip, vent their continuing anger on a young Arab, and kill the man by forcing him out of a window on the speeding train. Their crime is witnessed by Isabelle and reported to the police, enabling commissioner Couturier to find the killers. The major problem now is to prevent a race riot when right-wing extremists falsely accuse some Arabs of reprehensible actions and the townspeople gather to demonstrate at the prison.