Two girls meet on a train: Prune is looking for her father whom she has not seen since she was a little girl, Marina is looking for the mother she has never had. Prune learns that her father took his life and then she accidentally dies by drowning. Marina decides to assume her identity and begins a correspondence with Prune's mother.

Dans le train Paris-Lisbonne, Marina vient de tuer accidentellement son "ami" Bruno au cours d'une dispute. En remontant le couloir précipitamment, elle rencontre Prune, à la recherche de son père. Les deux jeunes femmes sympathisent, débarquent à Lisbonne...