The entire male population of Mesquite gathers around Pecos Kane's saloon when a new shipment of saloon girls arrives on the stagecoach. Johnny Nelson of the Bar-20 ranch falls instantly in love with passenger Mary Stevens, who is actually a schoolteacher. Kane informs her that the town she is headed for has burned down and offers her a job at the saloon, but Hopalong Cassidy saves her by pretending that his partner's wife, Mrs. Buck Peters, sent for her. Hopalong then asks Johnny to take Mary to the Bar-20. Along the way they see a stagecoach robbery, which has been engineered by Kane with help from corrupt Sheriff Sam Corwin, who informed him of a gold shipment on the stage. Johnny leaves Mary alone in the buckboard and intervenes in the robbery, during which he is injured by the robbers and is saved from death by Hopalong. They recognize a dead robber as one of Kane's gang. In the meantime, Hopalong's sidekick, Windy, has witnessed a killing at Kane's saloon. When the Bar-20 men gather for dinner, they agree that it is time to clean out the lawless element, namely Kane, and get together with neighboring rancher J. P. Ridley. Ridley has full confidence in Kane and Sheriff Corwin, however, and refuses to help them. While Johnny and Mary are flirting at an abandoned schoolhouse, the sheriff tries to arrest Johnny for the stagecoach robbery. Although Mary volunteers to testify as a witness on his behalf, Hopalong proves that the sheriff has no warrant and therefore cannot legally arrest Johnny. At Kane's saloon, Johnny identifies one of the robbers, and Hopalong insists the sheriff arrest him, but the outlaw pulls his gun and Hopalong shoots him in self-defense. During a dance at the Bar-20, Johnny becomes jealous when Hopalong dances with Mary and goes outside, where Kane's men emerge from the dark and kidnap him. When Hopalong goes outside to find Johnny, he also is captured, and the two men awaken at a campsite amidst a herd of cattle that have been rustled by Kane. In town, Kane and the sheriff convince Ridley that Hopalong and Johnny are responsible for the robbery, and encourage Ridley to sign a warrant to bring them in, dead or alive. Hopalong and Johnny extricate themselves from the ropes and take the sole guard hostage. As Kane has taken all the horses, they walk through the mountains until they reach a vast desert. Hopalong insists they cross, but before he and Johnny can start, the sheriff and two men arrive on horseback and are taken by surprise. After Hopalong and Johnny take the horses, they leave the sheriff and his men in the desert. The confession of Kane's man, as well as Hopalong's recent experience, convince Ridley to join their side. While Kane and his men shoot from inside, Johnny and Hopalong, with help from other ranchers, begin an assault on Kane's saloon. Unaware that Kane holds Mary hostage in the saloon, Hopalong throws in dynamite, and the saloon explodes. Although he is injured, Hopalong shoots Kane and Johnny rescues Mary. Hopalong survives and tells Ridley to give the reward to Johnny so he can set up house with Mary.