Jean Fournier (Claude Mann) is a young bank employee who 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 (Jeanne Moreau), divorced and mother to a child she rarely visits. Though Jackie also enjoys Jean's company, she constantly warns him that her passion for gambling will always be greater. Jean becomes jealous of not having all of her attention and has mixed feelings about gambling, yet he too is to some extend seduced by this new life style that involves taking risks. Despite Jackie's cool façade and alleged control over her choices - she claims she is unattached to the money itself, but rather the thrill of the game, and doesn't mind going from rich to poor in a matter of seconds -, she soon begins to reveal her vulnerability and the emptiness she often feels as result of her addiction.