Book The Binding Room — Nadine Matheson

The Serial Crimes Unit are called in to investigate when a local pastor is found stabbed to death. As DI Henley assesses the crime scene, she discovers a hidden door that conceals a room set up for torture – and bound to the bed in the middle of the room is the body of a man.

When another body is found, also tied down, Henley realises there's someone out there torturing innocent people and leaving them for dead. But why?

There's nothing that connects the victims. They didn't know each other. Their paths never crossed. But someone has targeted them, and it's up to Henley and the SCU to stop them before they find another binding room…