On Cormac Reilly’s first week on the police force, a detective calls him off traffic duty and sends him out to Kilmore to deal with a domestic issue.

After searching more than an hour in the gathering gloom, he finally finds the house. Completely dark, paint melting away and first floor windows boarded up, the house barely looks habitable.

When he knocks, a 15-year-old girl, slight with dark hair, opens the door. A small silent boy sits in front of a fire. The girl, Maude Blake, takes Cormac upstairs, past peeling wallpaper to a candle-lit room where a woman, clearly dead, lies on the bed. Skeletally thin, the woman has a shoelace tied around her left arm and there is a syringe on the floor beside her. An empty vodka bottle sits beside the guttering candle on the bedside table.

Due to the late hour, with social services closed, Cormac takes the children to the local hospital. The boy, Jack, is badly bruised. When he is examined, there are signs of multiple injuries in various states of healing. Maude asks about a restroom and then slips away and vanishes.

Twenty years later, Cormac hasn’t forgotten the case. After being a star detective in Dublin, he’s followed his partner, Emma, a research scientist, to Galway. He’s finding it a hard slog fitting in and mustering enthusiasm for the cold cases he’s assigned to.

Then Jack Blake is pulled dead from the river and listed as a suspected suicide. His sister turns up insisting that he didn’t kill himself. She has video evidence to support that. If the police don’t investigate, she threatens to go to the media.

Cormac is assigned to investigate the death of Maude’s and Jack’s mother, Honoria, although no one had been interested at the time. He’s specifically told to stay out of the investigation of Jack’s death. But soon, forces beyond his control overrun both cases.

This is a dark, moody book with many twists and turns. It will be compared to Tana French’s Dublin Murder Squad series. The Rúin doesn’t have the tight focus and forceful characters of the Tana French books, but it is absorbing, surprising and unexpected to the end.