An alarm sounds in the middle of the night for a burglary in progress at a winter-closed campsite in Bredäng, outside Stockholm.

The police spot a light in one of the farthest caravans and when the officers open the door they are greeted by a horrific sight. Floors, walls and furniture are completely covered in blood. A man has been killed with an axe and brutally dismembered.

On the floor lies a young man sleeping with a severed arm as a pillow. He is arrested and taken to Kronoberg prison, identified as seventeen-year-old Hugo Sand, the son of a famous writer.

Hugo suffers from a rare sleepwalking condition that is activated by nightmares. He is either the perpetrator or a witness, but claims to remember nothing from the night.

Detective Joona Linna contacts her old friend Erik Maria Bark to use hypnosis to try to find out what happened inside the caravan. So begins the sleepless hunt for a serial killer who is only just getting started . . .