Compton Castle is a Victorian psychiatric hospital long overdue for demolition. Its warrens of rooms and acres of grounds, originally designed as a sanctuary for the mentally ill, now provide the ideal stalking ground for a serial killer. Physically and mentally battered after his last case (Without Trace), Sergeant Trevor Joseph is a temporary inmate – but the hospital loses all therapeutic benefit when a corpse is dug out of a flowerbed. Then more bodies are found; young, female and both linked to the hospital. Everyone within the mouldering walls is in danger while a highly unpredictable malevolence remains at large. And, as patients and staff are interrogated by the police, the apparently motiveless killer watches and waits for the opportunity to strike again . . .