The accidental overturning of their "prairie schooner" kills a settler and his wife and leaves their little baby girl, Sunbeam, alone in the world. Discovered by Big Wolf, an Indian brave from a nearby tribe, Sunbeam is adopted and brought up as one of their number. Twelve years later Sunbeam is a beautiful girl and has been told of her parentage by Big Wolf who now loves her. One morning Bob Harris, a cowboy, and his pal are given a drink of water by Sunbeam. Mutual love springs up between she and Harris and she tells him she is not an Indian, but loves them for their goodness. Hiding in the rocks Big Wolf tries to kill the cowboy, but the bullet passes through his hat and he rides on unharmed. Filled with hatred and jealousy Big Wolf resolves that if he cannot have Sunbeam no one else shall win her. Making her a captive in her wigwam that night he ties her to the back of a wild bronco and drives it out upon the plains. In the early gray of morning Bob and his pal are herding the cattle when Bob catches sight of the girl on the bronco's back. Hastening to the corral he secures his lariat and informs the boys who dash out to the rescue. Realizing his plan has failed Big Wolf, who has been hiding nearby, attempts to stab Bob in the back, but is shot dead by one of the cowboys who catches sight of him in time. The bronco is captured and Sunbeam is carried back to the ranch unconscious by Bob. A few weeks later the assembled cowboys give Sunbeam and Harris a rousing send-off as they ride away to be married across the rolling hills.