Deputy U.S. Marshal Mac Bovard, known as the Hangman for his success at seeing guilty men die for their crimes, rounds up three of four outlaws suspected in a robbery that resulted in murder. Two are hanged. The third is needed to identify John Butterfield, whose face Bovard has never seen. Due to be hanged soon, the third outlaw refuses to cooperate. Knowing that Butterfield had been a U.S. Army cavalry trooper, Bovard goes to Butterfield's former post, Fort Kenton, to get assistance from the Army in identifying Butterfield.