Box's fourth novel featuring Cassie Dewell, the inspiration for the hit TV show Big Sky on ABC, comes to trade paperback.

She almost caught him once. Now he's back.

For three years, investigator Cassie Dewell has been on a hunt for a serial killer known as the Lizard King, whose hunting grounds are the highways and truck stops where runaways and prostitutes are most likely to vanish. Cassie almost caught him... once.

Working for the Bakken County, North Dakota, sheriff's department, Cassie has set what she believes is the perfect trap, luring him and his truck to a depot. But the plan goes horribly wrong, and the blame falls on Cassie. Disgraced, she loses her job and an inquiry into her role in the debacle is put into motion.

At the same time, Kyle Westergaard, a troubled kid whom Cassie has taken under her wing, has disappeared after telling people that he's going off on a long-planned adventure. Kyle's grandmother begs Cassie to find him and, with nothing else to do, Cassie agrees--all the while hunting the Lizard King.

Now Cassie is a lone wolf. And in the same way that two streams converge into a river, Kyle's disappearance may have a more sinister meaning than anyone realizes. With no allies, no support, and only her own wits to rely on, Cassie must take down a killer who is as ruthless as he is cunning. But can she do it alone, without losing her own humanity or her own life?