1950s, Mara a young prostitute travels by train with a foreign couple and their little girl. But a terrible collision with a freight train kills the parents. Mara takes the little one with her. She would like to adopt him but her social condition prevents her. She places the girl in an orphanage run by nuns, and decides to leave her current life, even if it means earning less money and working in exhausting conditions. She also gets rid of Carlo, a kind of small-scale pimp. Mara is having a hard time finding a job because the morality police continue to follow her. She appealed to the police commissioner who helped her place the girl in boarding school. This one finds him a job in a factory. But Mara's past emerges in the person of Giulio, her first love. The latter is convinced that the daughter Mara has is his daughter.