A mother and her son have been executed in their home and fingerprint matches show their attacker died 20 years ago. When CSI Darby McCormick is called to the crime scene, it's one of the most gruesome she's ever seen. But the forensic evidence is even more disturbing: someone watched the murder unfold - and the killer died in a shoot-out two decades earlier. The deeper Darby digs, the more horrors come to light. Her prime suspect is revealed as a serial killer on an enormous scale, with a past that's even more shocking than his crimes. Is it possible to steal an identity? Or are dead men walking in Darby's footsteps? The line between the living and the dead has never been finer.