Rocky Mountain Investigator Cassie Dewell has been on the trail of a serial killer she has named “the Lizard King” (aka Ronald Pelgram) who has left a string of victims in his wake across the terrain of North Dakota. She nearly caught him once and is determined to finish the job. She knows his habits and his favorite hunting ground: truck stops across the desert that provide a surfeit of unwitting victims. Now Cassie is spearheading a new plan, one she is certain will be successful, with the collaboration of local law enforcement including her fiancé, a Highway Serial Task Force, the FBI’s Critical Response Unit and other available agencies. They have set a trap that cannot fail to snare this wily prey.

With everyone in place, the countdown begins, the killer’s truck advancing toward the point of contact. Anticipating the end to a long and frustrating investigation, no one is prepared for a twist that upends all their expectations. Pelgram escapes once more his rendezvous with the law. The damage is excessive, the dead including Cassie’s fiancé. The failure is a blow not only to Cassie’s professional life but a personal tragedy, devastating her future and her place in the law enforcement community. Burying her emotions until there is time to process the extent of her loss, Cassie is cut loose, a woman without a badge or the authority to pursue a killer. Unfazed, she refuses to stop looking for the Lizard King.

Cassie Dewell made her bones in the Rocky Mountain landscape in a prior thriller (part of Box’s "Highway Quartet"). Working for the Bakken County sheriff’s department in North Dakota at the time her plan is conceived, the devoted investigator is positive her latest plan is foolproof, has left no stone unturned. It’s not. Cassie is stripped of her job, subject to an investigation by an FBI agent determined to put an end to her career. With only her wits and determination to put an end to the Lizard King’s rampage, Dewell understands the odds against her. They don’t matter.

Cassie’s search is complicated by a parallel pursuit: her search for troubled young Kyle Westergaard, a 14-year-old boy Cassie has taken under her wing. Kyle seems to have disappeared with an older friend, the boys apparently setting out on an adventure without leaving a note about where they have gone. Cassie promises Kyle’s grandmother she will try to find the boys as she pursues her serial killer, never suspecting that the boys might meet a stranger along the way, a man who will gleefully turn their adventure into a deadly encounter. Box segues between Dewell’s pursuit of Pelgram and the captive boy’s terror, at the mercy of an unpredictable, often violent man who demands absolute obedience. Kyle’s captivity and the menace that accompanies each day bring another layer to the tale--not only has Kyle run afoul of a murderer, but the potential for escape grows slimmer with each passing day.

Though I prefer Box’s Joe Pickett series, Cassie Dewell has similar traits, driven by a commitment to law enforcement and a love of the vast wilderness, the landscape often as challenging as the renegades creating murder and mayhem. Paradise Valley is a full-bodied thriller replete with agency rivalries and territorialism, all of which are forgotten when the prey is in sight. It’s a broad canvas with a rich assortment of personalities and events, from Dewell’s move to North Dakota with her 12-year-old son and colorful (outspoken) mother to Cassie’s decision to get married, from her obsession with capturing “the Lizard King” to the nightmarish results of his escape,  with Cassie in his sights and death in his heart. With heroes and villains, eccentrics and fools, killers and those who bring them to justice, Box claims this territory as his own.