Forensic psychiatrist Kate Myers believes the killer of two teenage girls in Bigler County, California, is the same man who savagely murdered her twin sister over fifteen years ago.

Deputy Sheriff Ben Slater hides his personal pain behind the job, but Kate's arrival in his county knocks his world on its axis. He wants to believe her wild theory, but the idea of a serial killer with the kind of pathology she proposes is too bizarre.

Together they work to find a killer whose roots began in a small town in Bigler County, but whose violence spread across the nation. A Janus-like killer, more monster than man, fixates on Kate. The killer wants nothing more than to kill "the purple-eyed girl again."