Paris. Jean Fournier, a young bank employee, is encouraged by his friend Caron to take an interest in gambling. After winning money in a game of roulette, he decides to vacation in Nice, where he falls in love with Jackie Demestre, an inveterate player. They start to gamble together and win lots of money. Jeanne Moreau, with her platinum blond hair, superbly embodies the uncontrollable passion for gambling.