Touchez Pas au Grisbi (1959)

Gentleman gangster Max and his partner, Riton, pull off their last, most successful heist and find themselves comfortable enough to retire in the style they enjoy. However, Max confides the details of the theft to his younger mistress, Josey -- who has secretly taken up with ambitious young rival gangster Angelo. Angelo then has Riton kidnapped and demands the stash of gold as ransom, which threatens Max's dreams of the perfect retirement.