Rancher's law
(Book)

"In a hot Arizona river basin, three bodies sway from ropes--executed by their fellow ranchers. Hundreds of miles away, in the muddy streets of Forth Smith, Arkansas, a deputy marshal hunts down a killer, the first of eight outlaws on his list. Now, the manhunter is about to be chosen for a mission to Arizona Territory. Major Gerald Bowen wants Luther Haskell to go undercover and find the truth about what happened. Bowen is on a campaign to bring law to the frontier, and Haskell is the right agent to investigate the deaths. But in Arizona, Luther comes up against a wall of silence and a family guarding a deadly secret. And in a land where some people get second chances and some don't get one at all, Luther Haskell must make his way through the good, the bad, and the damned--in pursuit of a cold-blooded killer with a plan of his own..."