The masked Death Riders that terrorize the Navajo shepherds are acting on behalf of a pair of gallows-birds, Ben Corliss and Timothy Slade. The ugly mugs do not appreciate meddlers: having discovered a rich emerald deposit on the Hopi reservation, they have enslaved the naïve Native Americans to their crooked goings-on, making them believe that the precious stones are magic and dispensers of prosperity. Tex and the pards put a spoke in their wheels: when he sees that things are taking a bad turn, Corliss kills his own partner and flees with a packsaddle full of emeralds, meeting a horrible death in the Painted Desert!