In a small, grim room, the body of a woman is discovered, panic and pain etched in her face. The scene matches in every detail a series of murders two years ago, murders that ended when irrefutable forensic evidence secured the conviction of a deeply disturbed young man named Derek Tyler.
But there's no way Tyler could have killed the latest victim. He's been locked up in a mental institution since his trial, barely speaking a word. So is there a copycat?
All his years of experience tell top criminal psychologist Dr. Tony Hill that there isn't, but that would make the murders literally impossible. While Hill tries to crack Tyler, DCI Carol Jordan and her team must mount a desperate undercover operation to trap the murderer, a decision that will have terrible consequences.
As the tension mounts, a mixture of psychological insight and dogged detective work leads inexorably to a terrifying climax where Tony faces one of the most perverse killers he has ever encountered.