Battle Mountain by C.J. Box

The campaign of destruction that Axel Soledad and Dallas Cates wreaked on Nate Romanowski and Joe Pickett left both men in tatters, especially Nate, who lost almost everything. Wondering if the civilized life left him vulnerable to attack, Nate dropped off the grid with his falcons in tow to prepare for vengeance.
When Joe gets a call from the governor asking for help finding his son-in-law, who has gone missing in the Sierra Madre mountain range, he enlists the help of a local, a rookie game warden named Susan Kany.
As Nate and fellow falconer Geronimo Jones circle closer to their prey, Joe and Susan follow the nearly cold trail to Warm Springs. Little do Nate and Joe know that their separate journeys are about to converge . . . at Battle Mountain.