Uninterested in his wife (Dirk Sanders), Ferdinand Griffon (Jean-Paul Belmondo) wearies of his stagnant life. But when the couple hires an enigmatic baby-sitter, Marianne Renoir (Anna Karina), Ferdinand falls head over heels in love with her and abandons his family. He soon discovers, however, that his mistress is not who she seems. Pursued by foreign thugs, Ferdinand and Marianne steal a car and embark on a crime spree through the French countryside all the way to the Mediterranean.