After years of cowboying, Charles A. Siringo had settled down to store-keeping in Caldwell, Kansas, when a blind phrenologist, traveling through, took the measure of his "mule head" and told him that he was "cut out" for detective work. Thereupon, Siringo joined the Pinkerton National Detective Agency in 1886. A Cowboy Detective chronicles his twenty-two years as an undercover operative in wilder parts of the West, where he rode with the lawless,...