Two large families anchor a town in the far north of France: the Momo Groseille family lives in squalid social housing on benefits and petty crime, while the Le Quesnoy clan—devout Catholics in a large detached house—are more orderly, with Monsieur Jean Le Quesnoy heading the regional electricity company and Madame Le Quesnoy tending the home and children. Yet they are both challenged by 12-year-old Bernadette, whose behavior strains the delicate balance of two very different worlds.
Twelve years earlier, on Christmas Eve, in a hospital where life is saved and futures are shaped, the obstetrician Docteur Mavial delivered two babies and returned home to his wife. The nurse—his lover, who hoped for a tender evening—swapped the babies, exchanging the Groseille girl for the Le Quesnoy boy. The misdeed remained hidden for years, only to cast a long shadow when the doctor’s wife dies and the nurse, still living with a secret, is rejected. She writes notes confessing her act to the Groseilles and the Le Quesnoys, and even to the obstetrician himself, who promptly leaves town to escape the fallout.
Facing the revelation, the Le Quesnoys decide to keep Bernadette in the dark and, in a drastic bid to stabilize their own precariousness, “adopt” Maurice as a son. They offer a substantial cash sum, plus free electricity, to the Groseille family. Maurice—who is diligent at school and well-behaved at home—begins quietly to rebuild a separate life: he purchases items from the Le Quesnoy household, stores away a hidden nest egg, and sends gifts back to his former family and friends, all while maintaining a careful distance from the truth. The awakening moment comes when Bernadette declares that she hates poor people, and Maurice finally reveals her origins, shattering the illusion of belonging to one clean, respectable world. She sneaks to the Groseille home, is confronted by what she sees, and retreats to the Le Quesnoy mansion, locking herself away for weeks.
Maurice remains in touch with the Groseilles, quietly assisting them by removing things from the Le Quesnoy home and, on one occasion, arranging a gathering by the river for all the children of the two families (except the still-secluded Bernadette) to drink beer and swim. The moment of cross-class connection comes when the eldest Le Quesnoy boy shares a fleeting, stunned intimacy with the eldest Groseille girl, a sign of how fragile boundaries between the two households have become.
Returning home from the river, the Le Quesnoy children’ antics trigger a crisis: Madame Le Quesnoy suffers a nervous breakdown and turns to alcohol. Bernadette runs away, only to be found and brought back by the police. Monsieur Le Quesnoy moves her, along with the pregnant maid who cannot reveal the lover she has, to a seaside cottage, with the rest of the family to follow after the school term ends. Nearby, in an adjoining seaside cottage, the nurse lingers, and the obstetrician finally gets to spend time with her after he has suffered a stroke, bringing the hidden past into sharper focus as the two worlds—one of privilege and one of poverty—brush against each other in a landscape of shorelines and secrets.
