In Plain Sight - C. J. Box

Spring has finally come to Saddlestring, Wyoming, and game warden Joe Pickett is relieved the long, harsh winter is over. However, a dark cloud threatens to spoil the milder weather. Local ranch owner and matriarch Opal Scarlett has vanished under suspicious circumstances. Two of her sons, Hank and Arlen, are battling for control of their mother's multi-million-dollar empire, and their bitter fight threatens to tear the whole town apart.
Everyone is so caught up in the brothers' battle that they seem to have forgotten that Opal is still missing. Joe is convinced, though, that one of the brothers murdered their mother.
Determined to uncover the truth, he is attacked and nearly beaten to death by Hank Scarlett's new right-hand man on the ranch - a recently arrived stranger who looks eerily familiar...
A series of threatening messages and attempts to sabotage Joe's career follow. At first, he thinks the attacks are connected with his investigation of Opal's disappearance, but he soon learns that someone else is after him - someone with a very personal grudge who wants to make Joe pay... and pay dearly.