It begins with a murdered child. It ends in a valley where nightmares are born.

When Detective Inspector Amaia Salazar is called in to investigate the death of a baby girl, she finds an ominous sign that points to murder. The girl's grandmother tells the police that the 'Inguma' was responsible - an evil demon of Basque mythology that kills people in their sleep - Amaia is forced to return to the Baztán valley for answers. Back where it all began, she comes face to face with a ghost from her past. And finally uncovers a devastating truth that has ravaged the valley for years.