Resentful college graduate Eagle Eye, disguises himself as a white man and persuades James Harbison to create a new breed of cattle by crossing cows with bison. The first of the strain, a wild bull called Diablo, escapes from Harbison's ranch and goes to Skull Mountain, headquarters of a band of savage Indians led by Eagle Eye and dedicated to the destruction of the white man. Eagle Eye trains the bull to lead away the rancher's cattle and to gore anyone who attempts to stop him. Dan Allen is sent by the government to investigate and goes to the Harbison ranch, where he falls in love with Eleanor, the rancher's pretty daughter. Eagle Eye lures Harbison and his daughter to Skull Mountain and sets Diablo loose on them; Dan arrives and overcomes the bull. All ends well and Dan marries Eleanor.