A repentant gambler, Simon is a senior inspector in the banditry repression brigade headed by his friend Pierre Tramoni. Pierre is brilliant and wants to go far. Simon has no ambition and only one passion: gambling. For several months, Simon has been trying to catch the Djian brothers, young and dangerous bank robbers, in the act. He fails but discovers, through an informer, strange links between Pierre and the Djians, during his investigation which leads him back to the gambling halls. When the Djians finally fall, the treachery of Commissioner Tramoni is revealed.