The Golden Girl Mine, owned by Randall (Frank Ball) and Furman (Hal Price), is suffering great losses, as their gold shipments by stagecoach are being held up and stolen. The only clue is a horse called White Peril, ridden by the masked outlaw leader at every hold-up. Strangely enough, the horse is owned by Rndall's daughter, Joan (Claire Rochelle), the only one known to be able to ride the horse. Bob MacArthur (Bob Steele) becomes the deputy of Sheriff Carson (Steve Clark), and hires himself out to the Lazy-R ranch. There, he makes an enemy of "Dusty" Williams (Charles King), a neighboring rancher, when he is kept from shooting White Peril. Peters (Ernie Adams), the ranch foreman, makes himself helpful to Bob, answering all questions concerning the robberies, murders and White Peril. Bob follows White Peril to the outlaw's hideout, only to be captured. "Dusty", revealed as the masked chief's head henchman, leaves Bob to be killed by his henchmen, but he escapes after being led to believe that Joan is the masked chief. After a fast chase, another stagecoach robbery and a chase on a railroad handcar, Bob brings the masked chief, who is John Doe, to justice and who had owned White Peril as a colt, and was able to ride him unknown to anyone.