A self-assured businessman murders his employer, husband of his mistress, which unintentionally provokes an ill-fated chain of events.

This loosely plotted coming-of-age tale follows the life of 15-year-old Laurent Chevalier as he stumbles his way over the burgeoning swell of adolescence in 1950s France. After having his first sexual experience with a prostitute and dodging the lips of a priest, Chevalier contracts a case of scarlet fever. When the fever leaves him with a heart murmur, Chevalier is placed in a sanatorium, along with his over-attentive and adulterous mother.

Ginette Chaluzac, who has left Central France for Paris, now works as a seamstress in a modest workshop in the Marais district. Her life is quiet and uneventful until the day when, to her surprise, she receives a letter containing a hundred-franc banknote. The sender, who remains anonymous, renews his gift day after day and Ginette grows accustomed to the situation. Her material situation improves but after a while she starts asking herself questions about the one who sends her the money and his/her intentions. Till obsession. To make it clear in her mind she eventually decides to investigate...