A murdered child in the remote Baztán valley triggers a return to a past Inspector Amaia Salazar cannot escape. Called to investigate the death of a baby girl, Inspector Amaia Salazar discovers an ominous sign pointing to murder, and a local legend of the 'Inguma,' an evil demon that kills in its sleep. Forced to confront a ghost from her past and the dark history of the valley, Amaia uncovers a devastating truth that has plagued the region for years. The narrative unfolds through Amaia's perspective as she navigates the treacherous landscape of both the physical valley and her own memories.

The final installment of Dolores Redondo's Baztan trilogy has been lauded for its masterful storytelling and atmospheric suspense, drawing comparisons to acclaimed Scandinavian crime dramas. Critics have highlighted the intricate plotting and the compelling character of Inspector Amaia Salazar as key strengths. The novel effectively blends elements of crime investigation with folklore and supernatural undertones, creating a unique and immersive reading experience. Its conclusion to the trilogy has been noted for its satisfying resolution of long-standing mysteries within the series.