A young woman survives a great white shark attack, whilst on a family boating vacation, however soon realizes the nightmare is far from over. Those around her can not be trusted, and she must face her demons, if she is to step back in the water.

When the naked body of a teenage girl is found on the banks of the River Baztán, it is quickly linked to a similar murder one month before. Soon, rumours are flying in the nearby village of Elizondo. Is this the work of a ritualistic killer or is it the basajaun, the ‘invisible guardian’ of Basque mythology? Inspector Amaia Salazar leads the investigation, taking her back to the heart of the Basque country where she was born, and where she hoped never to return. Shrouded in mist and surrounded by impenetrable forests, it is a place of unresolved conflicts and a terrible secret from Amaia’s childhood that will come back to haunt her. Faced with the superstitions of the village, Amaia must fight the demons of her past to confront the reality of a serial killer on the loose. But as she is drawn deeper into the investigation, she feels the presence of something darker lurking in the shadows…

A battered young girl finds refuge in a mysterious button, with unprecedented consequences....