When shifty cattlemen Belknap (Walter Miller) and H.R. Shelby (Gordon Hart) are caught shipping infected animals to Mexico, they frame inspector Gene Autry. Now Autry and his sidekick, Frog Millhouse (Smiley Burnette), must catch the bad guys in the act and set things straight. June Storey co-stars as rancher Martha Wheeler. Autry sings "I'm Gonna Round Up My Blues," "Moonlight on the Ranch House" and "Big Bull Frog."