Galway 1993: Young Garda Cormac Reilly is called to a scene he will never forget. Two silent, neglected children - fifteen-year-old Maude and five-year-old Jack - are waiting for him at a crumbling country house. Upstairs, their mother lies dead.
Twenty years later, a body surfaces in the icy black waters of the River Corrib. At first, it looks like an open-and-shut case, but then doubt is cast on the investigation's findings - and the integrity of the police.
Cormac is thrown back into the cold case that has haunted him his entire career - what links the two deaths, two decades apart? As he navigates his way through police politics and the ghosts of the past, Detective Reilly uncovers shocking secrets and finds himself questioning who among his colleagues he can trust.
What really did happen in that house where he first met Maude and Jack? The Ruin draws us deep into the dark heart of Ireland and asks who will protect you when the authorities can't - or won't.