In Paris, Bob Montagne (Roger Duchesne) is practically synonymous with gambling -- and winning. He is kind, classy and well-liked by virtually everyone in town, including police inspector Ledru (Guy Decomble). However, when Bob's luck turns sour, he begins to lose friends and makes the most desperate gamble of his life: to rob the Deauville casino during Grand Prix weekend, when the vaults are full. Unfortunately, Bob soon learns that the game is rigged and the cops are on to him.