The light spilling in from the corridor would have to do. Though weak, it was sufficient to show Aldís a boy sitting in the gloom at the farthest table. He had his back to her, so she couldn't see who it was but could tell that he was one of the youngest.

A chill ran down her spine when he spoke again without turning, as if he had eyes in the back of his head. 'Go away. Leave me alone.'

'Come on. You shouldn't be here.' Aldís spoke gently, fairly sure now that the boy must be delirious. Confused rather than dangerous. He turned, slowly and deliberately, and she glimpsed black eyes in a pale face. 'I wasn't talking to you.'

Aldis is working in a juvenile detention centre in rural Iceland. She witnesses something deeply disturbing in the middle of the night; soon afterwards two of the boys at the centre are dead.

Decades later single father Odinn is looking into alleged abuse at the centre following the unexplained death of the colleague who was previously running the investigation. The more he finds out, though, the more it seems the odd events of the 1970s are linked to the accident that killed his ex-wife. Was her death something more sinister?

Yrsa Sigurdardottir is a huge European best seller with both her crime and her horror novels. You might want to sleep with the light on after listening to The Undesired.