Filmed on locations at Joshua Tree National Monument and Chatsworth, CA, this surviving Rin Tin Tin melodrama features the famous canine as Lobo, the "half-breed" leader of a pack of wolves. When forest fires ruin their habitat, the starving animals trek down into the desert, where they in desperation attack the local cattle. Wounded by a treacherous cactus, Lobo is nursed back to health by young borax prospector Dave Weston (Charles Farrell), but is forced to wear a disguise lest he becomes the target of the irate ranchers. Nasty Borax Horton (Pat Hartigan), a claim jumper masquerading as the town chemist, becomes a threat to both the dog, who has a $100 reward on his head, and Weston, who has struck pure borax. On his way to stake his claim, Weston is followed by Horton, who seriously wounds him in a fight. Lobo, however, manages to alert Dave's girlfriend, May Barstow (June Marlowe), and Horton gets his just dessert.