La vie est un long fleuve tranquille

In a maternity clinic two children from families with completely different social backgrounds are switched at birth. One goes on to live in an upper-middle-class family while the other to a poor family. Twelve years later, the mistake is discovered and the child living with the poor family is taken back by his parents, but keeps in touch with his former family and makes them encounter his new brothers and sisters. A series of satirical and comedic scenes follow.