 This 31st entry of the 66 films in the Hopalong Cassidy series marks the first of 35 consecutive appearances, in the remaining films of the series, of Scottish-born comedian Andy Clyde in the role of "California Carlson", although his introduction in this film is as "California Jack" Carlson and his credentials won t bear much scrutiny. The film finds local officers in an outlaw-infested town in California helpless to cope with the situation and a citizens committee comes to Texas and appeals to the Texas Rangers for help in organizing the forces of law and order. Captain Andrews (Morgan Wallace) of the Rangers offers the assignment to Hopalong Cassidy (William Boyd) and Lucky Jenkins (Russell Hayden), but Cassidy, whose period of service in the Rangers is almost over, refuses. The as-usual impetuous Lucky takes the job alone. While on patrol duty, Cassidy is following the trail of a large herd of rustled horses and discovers the hide-out of the Bruce Morgan (Morris Ankrum) gang. The place is deserted except for a garrulous old cook who calls himself "California Jack" Carlson, who receives Cassidy who is posing as a Morgan friend and fellow outlaw Ben Stokes (Glenn Strange), whom California does not know. Cassidy arrests the frightened cook as a material witness against the gang and starts for Texas Ranger headquarters. Learning from Carlson that Morgan had planned to leave for the west coast, Cassidy gets permission from Captain Andrews to take up the trail. He is made a U. S. Marshal, which gives him blanket authority, and Carlson is taken along as a guide. Cassidy arrives in Santa Carmen, California just when newly-appointed town sheriff Lucky is foolishly setting out single-haned against Morgan and his gang. Cassidy and California join him and escape following a fight in which Lucky is wounded. They find refuge at the hide-out of Pico Serrano (Thornton Edwards), once rich but now penniless, as he and other Californians have been cheated out of and driven from their homes by the unscrupulous Morgan and his gunmen. Lucky falls in love with Pico s daughter, Paquita (Esther Estrella.) Cassidy organizes a posse and engages Morgan and his gang in a gun fight. Morgan, Stokes and others of the gang storm Pico s hide-out and, during the fighting, Paquita is mortally wounded and dies in Lucky s arms. With an augemented posse, Cassidy again invades Santa Carmen and, following a spectacular fight, Pico kills Morgan, while Gardner (Dick Curtis) and Stokes are taken prisoners.