When poisonous devil-weed infects the grazing lands of cattle country, misguided ranchers , including George Larrabee (Robert Homans), burn off every acre of the infected area-the wrong thing to do. The State Agricultural Commission sends inspector Gene Autry (Gene Autry) and his pal Frog Millhouse (Smiley Burnette) to look into the problem but they encounter strong opposition and are even mistaken for bank robbers when they are found in possession of cash from a crashed crop-duster airplane whose pilot, Jerry Willis (Eddie Dean), they were only trying to help. Against all the opposition, Gene eventually persuades the ranchers chemical spraying is the only way to rid the grazing land of the devil-weed while also romancing the rancher's daughter, Sue Larrabee (Fay McKenzie) and saving the cattle from a fiery stampede.