When Spaniard Don Luis de Serrano (George Douglas) produces a deed entitling him to most of the land in the American Southwest, the Three Mesquiteers -- Stony Brooke (John Wayne), Tucson Smith (Ray Corrigan) and Lullaby Joslin (Max Terhune) -- find themselves displaced from their ranch and subjected to heavy taxation. While battling de Serrano's ruthless henchmen, the Mesquiteers struggle to debunk the dubious document at the center of the Spaniard's scheme.