Nicole (Agnes Soral) is sent up the river for infanticide in this routine woman-in-prison feature. There she meets Marthe (Annie Girardot), a fellow murderess who receives special treatment from the warden Dessombes (Marie-Christine Barrault). The warden frames Nelly (Bernadette Lafont) for drug possession and has her thrown into solitary confinement. Sabien (Corinne Touzet) is a newcomer convicted of armed robbery who latches on to the lesbian Lucie (Milva), a longtime prisoner slated for release.

A 40-year-old mechanic whistles at a passing teenager; she stops and upbraids him. In embarrassment, he claims he was whistling at her companion, her 14-year-old cousin, Isabelle. This changes Isabelle's outlook on life: her favorite story is Anderson's "Little Mermaid," and she thinks that in Georges she's found her prince. She follows him, engages him in conversation, and turns up at his flat. At first, he pushes her away and tells her she's nuts, but slowly he finds that she brings out of him a playful self, and he likes her devotion. The attraction builds, threatening Georges' adult relationships, including that with Nelly, his sweetheart. Where on earth can this affair lead?

Guillaume, thirty years old, a man of images who never goes out without a filming device, decides one morning to take a voyage to Rouen empty-handed.