Compton, Ralph. Sundown Riders.

"After years as a professional gambler--and a deadly shootout on a riverboat casino--Tom Calvert and his young protégé, Asher Smith, have survived an arduous journey across the frontier to Friendly Field, Idaho. The bucolic Quaker community welcomes them with open arms, and soon Tom is courting a widow and learning, to his surprise, to enjoy the quiet life. Then an elder of Friendly Field is found murdered, and the townsfolk start whispering about the work of the devil. Tom doesn't believe in the devil, just the evil that men do, and he resolves to solve the gruesome crime before fear causes the people of peaceful little Friendly Field to turn against one another"--Provided by publisher