Penny, the young protagonist of this autobiographical novel, has fled the family home aboard a train that runs through an underground city. This journey, at times, seems like an immersion in her own conscience: the pitfalls that her bourgeois education generates in her personality, the scope of religion in shaping her morals, the sexual formation of women and the role assigned to them in 1960 Italy, and the need to position oneself on the side of the oppressed.