A murdered child, marked with an ominous sign, forces Inspector Amaia Salazar back to the valley of her past to confront an ancient evil. The death of a baby girl, with a suspicious mark across her face, points to murder and a potential link to the Inguma, an evil demon from Basque mythology that kills people in their sleep. As Amaia returns to the Baztan valley, a place where nightmares are born, she must confront a ghost from her past amidst a blizzard. She is driven to uncover a devastating truth that has ravaged the valley for years, bringing the trilogy to its atmospheric conclusion.

This final installment in Dolores Redondo's bestselling Baztan trilogy is noted for its atmospheric storytelling and compelling detective, Amaia Salazar. The novel masterfully blends crime investigation with elements of Basque mythology and gothic horror, creating a suspenseful narrative. Readers have praised its ability to bring the series to a satisfying and dark conclusion, delving into the valley's deepest secrets. The book has been recognized for its intricate plot and its rich evocation of place, solidifying its status as a significant European crime series.