Joe Wallace is shot down as he races to inform Roy Rogers about thugs responsible for a recent cattle stampede in Duane County. Old Joe dies before he can impart the information. Investigating the murder, Roy follows a trail of clues which leads to VictorMarsh, president of the Cattleman's Association. Marsh is trying to stir up hostilities between cattlemen and sheepherders so that he can seize the valuable grazing rights in the territory. But Rogers will need to turn up evidence fast, before an all-outrange war erupts.