Unable to apprehend the train-robbing Smith Brothers, Sheriff Doc Shores calls the Pinkerton Detective Agency for assistance. The agency sends Charles Siringo, an undercover specialist known for his unorthodox methods of capturing criminals. Without any real leads, Siringo travels to the Smith Family farm, posing as a laborer looking for work. While there, he charms the Smith Brothers’ little sister into revealing information on their whereabouts. The brothers are soon arrested in Utah, but there’s no stolen money connecting them to the crime. Stuck with a weak case, Siringo has one more ace up his sleeve. He goes undercover again, this time posing as a criminal in the jail cell with the Smith Brothers in hopes they’ll confess. It’s a desperate and dangerous ploy, but it’s the only card Siringo and Shores have left to play. Years later, Doc Shores catches up with gunfighter-turned-reporter Bat Masterson to tell the whole story.