After failing to capture the ruthless murderer Augustine Chacon on U.S. soil, Arizona Ranger Burton Mossman temporarily relinquishes his badge to chase him across the border. In Mexico, Mossman strongarms a two-bit criminal named Burt Alvord into revealing Chacon’s hideout, and he goes undercover as a horse thief to penetrate Chacon’s gang. With the trap set, Mossman waits for the perfect moment to spring, but the crafty Chacon is already onto his ruse. In an epic showdown, Mossman makes his final play to capture his man. Years later, gunfighter-turned-newspaperman Bat Masterson visits the Yuma Territorial Prison to meet with Burt Alvord, the only eyewitness, to get the real story of Mossman’s relentless pursuit.