Caleb's brother, Anton, has been missing for months. After almost giving up hope of finding him, Caleb receives an anonymous message - a man has been shot and Ant might be next. He tracks his brother to an isolated island where he finds a secretive community under threat from a sniper, and a cult-like doctor with a troubling background. When body parts begin to wash up on shore, it looks like the sniper is growing more desperate ... Her fans includeJane Harper, Eva Dolan and Ian Rankin.