Juan de Dios O'Rourke, an American Secret Service, of Spanish-Irish descent, leads the cattle ranchers and border patrol in a fight to suppress a gang of cattle rustlers, who have been driving large herds north-to-south from Texas into Mexico, and smuggling illegal, no-passport Chinese aliens south-to-north from Mexico into Texas, operating from a rambling mansion on the Texas side of the border, aided by his sweetheart, a rancher's daughter, Phoebe Joyce.