With local officials helpless to cope with the outlaws that are infesting their town, the citizens committee appeals to the Texas Rangers to send an experienced man to organize the forces of law and order. Captain Andrews offers the assignment to Hopalong Cassidy and Lucky Jenkins, but Cassidy, whose service is almost at an end, refuses, and Lucky takes the job alone. After resuming his patrol duties, Cassidy comes upon a dying wrangler and learns that a large herd of horses has been stolen. Following the trail of the rustled herd, Cassidy discovers the hideout of Gardner and his gang. The place is deserted except for the cook, Carlson, who calls himself California. Not suspecting that Cassidy is a lawman, California receives him as Ben Stokes, a notorious outlaw and friend of Gardner. Cassidy arrests California as a material witness against the gang and starts for headquarters. When Gardner's attempt to silence California fails, California switches his allegiance to the law. Learning that Gardner is heading for the West Coast, Cassidy takes up his trail with California as his guide. They arrive in the town of Santa Carmen at the moment that Lucky is about to face Gardner, who has teamed up with outlaw Bruce Morgan. Cassidy and California join Lucky and, following a fight in which Lucky is wounded, they all manage to escape. The three find refuge at the hideout of Pico Serranno who, along with the other citizens of Santa Carmen, have been cheated out of their homes by the unscrupulous Morgan and his gunmen. While Lucky falls in love with Pico's daughter Paquita, Cassidy organizes a posse of citizens and apprehends some of Morgan's men, whom Pico then insists upon hanging. In response, Stokes, Morgan and the others storm Pico's hideout and fatally wound Paquita, who dies in Pico's arms. Cassidy then recruits a larger posse to apprehend the outlaws, and in a spectacular shootout, Pico kills Morgan while Stokes and the others are taken prisoners.