Pilote de guerre en Indochine, Pierre croit avoir tué une petite fille en bombardant un village. Quelques années plus tard, sur le quai de la gare de Ville-d'Avray où il accompagne son amie Madeleine, il rencontre Françoise, une fillette de 12 ans, abandonnée par sa mère et que son père a placé dans une institution religieuse. Se faisant passer pour lui, Pierre prend l'habitude de la sortir tous les dimanches. Une tendre et pure amitié s'établit entre eux. Mais les braves gens s'inquietent.
Pierre, a former military pilot whose plane crashed after a bombing raid in Indochina (killing a little girl in the process), just returned home to France from the French-Indonesian war. Suffering from delayed stress and partial amnesia, the young man leads a pointless life - until he meets a 12 year old orphan girl who has been left at a local convent school. Posing as her father, Pierre contrives to meet the girl every Sunday, and a warm attachment develops between the two - but their innocent friendship is misread by nearly everyone, even people who know Pierre well, and eventually friends become suspicious of their relationship, and tragedy follows.