Diamonds Are Brittle (1965)

Bernard Noblet, a modest bank clerk in Geneva, Switzerland, is bored to death. His schoolteacher fiancee Juliette and his inventor friend Roger, unsuccessful despite his efforts, also dream of a spicier life. One day, they decide to rob a bank together to get enough money to lead the good life. But then, Bernard meets Bettina and her mother, professionals in the field. Why not let them and their gang do the heist they are planning against a nearby jewelry boutique and collect afterwards? A police alarm and a billiard from Roger's club to hide the loot should do the trick.