Canfield, respected rancher, is involved in crooked horse racing, and also leads an outlaw gang! Some 10 years before our story, the gang raided an isolated cabin, leaving 5-year-old Frankie an orphan. The boy grows up wild, his only friends the wild horses...now joined by El Diablo, a savage but very fast race horse that Canfield steals and loses, in the process killing ranger Elliott Norton. Norton's ranger brother Bob now appears in the region to find his brother's killer; menaced by the outlaws, the vigilantes, and the Devil Horse, his only chance may be to enlist the aid of the now-speechless Wild Boy.