Cathy decides to take revenge on two con men, Bontemps and Lachard, who were responsible for the bankruptcy and ruin of her father. She asks Michel, her ex-husband, to help. There is no other solution for them than to become crooks themselves, so they conceive a shady deal with Bontemps on an island in Brittany. The first part of their plan is a success and they leave with a huge sum of money. The second part is to take place in Monte Carlo, where they can expect a dramatic showdown with Lachard...