West of Sonora

On her way to visit her grandfather, Jeff Clinton, the sheriff of Sico City, little orphaned Penelope Clinton is abducted by her maternal grandfather, the outcast Black Murphy whose, name is associated with a reign of lawlessness that has plagued the territory. The Clinton and Murphy families have been locked in an age-old feud, and consequently, Jeff vows to bring Murphy to justice. To aid in his quest, Jeff deputizes his old friend Steve Rollins, who suspects that the family feud may be fueling Jeff's zeal. One day, Steve rides out to inspect a rich gold strike made by prospector Jack Bascom. As Steve nears Bascom's mine, he finds Bascom under siege by looters. After driving off Bascom's assailants, Steve straps the gravely wounded Bascom onto his horse and takes him to Murphy's nearby camp. After operating on Bascom to save his life, Murphy releases Steve on the condition that he never reveal the location of the camp. Upon returning to town, Steve tells Jeff that he has seen Penny and vouches for Murphy's integrity. After Steve proposes a meeting between Jeff and Murphy, Jeff's brother Sandy urges Jeff to accept Steve's offer and thus trick him into leading them to Murphy's hideout. Unknown to Jeff, Sandy is the covert leader of a band of renegades who have been committing crimes in Murphy's name. As Steve and Jeff near Murphy's camp, Sandy appears with his men and declares his intentions to ambush Murphy at Stone Canyon. After ducking into the woods, Steve emerges as his alter ego, the masked rider of justice known as The Durango Kid, and warns Murphy of the ambush. The Durango Kid then thwarts the confrontation by returning Penny to Jeff. Wanting to claim the Bascom mine for himself, Sandy kills the old prospector and then blames the murder on Murphy. Soon after, Murphy comes to Jeff's office to demand Penny's return. Drawing his pistol, Steve wounds Murphy, and Jeff promptly jails him. When Sandy and his accomplices, Brock and Dickson, incite a mob to lynch Murphy, The Durango Kid appears just in time to rescue him from the crowd and free him. Afterward, Jeff throws a welcome party for Penny and there Steve reveals that Bascom has bequeathed his mine to the little girl. Realizing that Penny's newfound fortune may endanger her life, Steve assigns his friend Smiley Burnette to be her bodyguard. Determined to destroy the record of Penny's claim, Sandy sets fire to the land registration office. When Sandy discovers that Steve had removed the records for safekeeping, he suggests that Jeff ride unaccompanied to the Bascom mine to investigate. Planning to murder both his brother and Penny and then lay claim to the mine, Sandy and his men wait in ambush for Jeff. Steve, meanwhile, learns from Smiley that Jeff has gone to the mine and realizes his peril. Jeff arrives at the mine to find Murphy there, and as Sandy has his men train their guns on them, The Durango Kid gallops up just in time to shield Jeff and Murphy. Sandy then rides back to town to kill Penny, but The Durango Kid is alerted to the little girl's danger. Drawing the outlaws' gunfire, The Durango Kid allows Murphy and Jeff to escape and then apprehends Brock, who admits that Sandy killed Bascom. At the Clinton home, Sandy sends Smiley on a wild goose chase while he prepares to murder Penny. Just then, The Durango Kid bursts in and overpowers him. Following closely behind, Jeff and Murphy rush in and hug their granddaughter. Their mission accomplished, Smiley and Steve bid the reconstituted family goodbye and head for Texas.