Since the dark events that scarred her childhood, Kier Templer escaped her hometown to live life on the road. She and her twin have never lost contact until, on a trip to a Portuguese national park, Kier vanishes without a trace. Detective Elin Warner arrives in the same park ready to immerse herself in its vast wilderness - only to hear about Kier's disappearance, and discover a disturbing map she left behind. The few strangers at an isolated campsite...

When two serial killers--Efrem Judah Goode, imprisoned in Tennessee, and the Broken Heart Killer--are locked in a twisted rivalry, FBI profiler Caitlin Hendrix must unravel the connection between them, trapping her between a manipulative psychopath and a ruthless UNSUB and forcing her to dive into two dark and depraved minds.