This novel concludes a cycle that the author calls The Cemetery of Forgotten Books, a saga with interconnected characters and storylines. In this case, the author sets the story in Barcelona at the end of the 1950s. The story focuses on a family of booksellers, the Sempere family. Alicia Gris receives an official assignment in Madrid to find the whereabouts of a minister from Franco's government who has mysteriously disappeared. The initial clues will soon lead her to Barcelona, to dark years in which prisoners from the Montjuïc prison were tortured.
The author takes a clear stance in criticizing the Francoist regime, highlighting the violence and cruelty, described realistically, against its opponents. On the other hand, Zafón gives his semi-Christian characters a persuasive ability that may harm less educated readers. The book contains several irreverent phrases and a somewhat erotic scene.