Some murder cases you can't forget, no matter how hard you try. For Detective Matt Buchanan, it's the death of fourteen-year-old Samantha Coates. And there have been other missing girls since; the litany of violence never stops. He's probably been in the job too long, Buchanan reckons, and has taken a gutful of the nastiness of human nature. But when he pursues some fresh leads, it soon becomes clear he's on the trail of something big. As he pieces the horrific crimes together, Buchanan finds the very foundations of everything he once believed in start to crumble. Taking the law into his own hands, he's forced across that grey line that separates right and wrong - into places so dark, even he might not make it back...