The Three Mesquiteers, led by Stony Brooke (John Wayne), Tucson Smith (Ray Corrigan), and Lullaby Joslin (Max Terhune), become mysterious "night riders" to fight against Talbot Pierce's (George Douglas) evil schemes. He has faked a land title to 13 million acres in the name of Don Luis de Serrano, imposing high rental rates on ranchers and threatening those who can't pay with confiscation of their cattle. The Mesquiteers help rancher Susan Randall (Ruth Rogers) evade heavy taxes, don disguises as "Los Capaqueros," and start robbing tax collectors to distribute the money to the ranchers. As they gather evidence against de Serrano, they outsmart him and ultimately bring him to justice, with the help of a mob of townsfolk and ranchers.