Hopalong Cassidy, boss of the BAR 20 ranch in Texas, rides down the New Mexico cattle country in response to an urgent message from his lifelong sweetheart, Nora Blake, who is in serious trouble. Before he, "Lucky" Jenkins and Pappy can reach her ranch, they are stopped by Clay Allison, a cattle-rustler who is in almost complete control of the district, and wants to extend his holdings by seizing Nora's cattle and driving her out.