Paris, 1956. Everything is going smoothly for Roger, married to Denise, and Paul, married to Monique, until the day they win a house in a radio contest. The difficulties of living together and the intrusion of their parents-in-law lead to a falling out.

Marc, a motorcycle brigadier, is engaged to the charming Véronique. But his future brother-in-law, the clumsy Roger, leader of a Sunday motorcycle gang, has set his sights on joining the motorcycle police.