After out-of-work cowpunchers Bob Banning and Chito Rafferty fix the wagon wheel of Arizona miner Ben Jason, Ben gives them a gold nugget in thanks. In Rim Rock, Bob and Chito take the nugget to assayer Matt Wyatt, who eagerly gives them fifty dollars for it. As soon as the cowboys leave his office, Wyatt compares the nugget to an ore sample he keeps in a drawer and realizes that Ben has found the much sought-after "Lost Dutchman" mine. On the street, Wyatt then overhears Ben discussing his valuable claim with his niece Judy, who has just arrived in town, and sees him pocket a map to the place. Excited, Wyatt rushes to tell Morgan, the crooked Rim Rock saloon owner, about the mine and suggests that they steal the map and Ben's money belt before he can register his claim in nearby Trinity. Morgan agrees to the plan and takes Rocky, one of his men, to intercept Ben as he rides to Trinity. When Ben and Judy become aware that they are being followed, Ben sends Judy ahead, while he stays to face the men. After a brief shootout, Morgan and Rocky kill Morgan, steal his map and money belt and ride off. At the same time, Bob and Chito are riding nearby and, hearing gun fire, rush to the scene. They arrive moments ahead of Judy and the sheriff and, despite their protests of innocence, are arrested for Ben's murder. While Bob and Chito sit in the Rim Rock jail, saloon girl Dixie, one of Chito's paramours, asks Morgan for an advance on her salary so that she can bail Chito out. Before Dixie can legally free Chito, however, Chito and Bob escape by setting a fire in their cell. Determined to clear themselves, Chito and Bob ride to the site of Ben's murder to search for his money belt, and run into Judy there. The cowboys eventually convince the wary Judy, who is also looking for her uncle's money belt, of their innocence. Realizing that Wyatt was the only other person who knew about the Ben's gold, Bob and Chito ride back to Rim Rock to question him. Although Wyatt, whom Morgan has double-crossed, denies any involvement in the crime, Bob senses his guilt and starts to beat him. When Chito alerts him to the sheriff's presence, Bob stops fighting, but spies on Wyatt as he runs to confront Morgan. Dixie then informs Bob that she saw Ben's money belt in Morgan's office, and he sneaks into Morgan's office just as Wyatt is forcing the saloon owner to open his safe. As Bob and Morgan then fight, Wyatt takes the map out of the money belt and flees with it. After Bob knocks Morgan out and out-manuevers Rocky and his cohorts, he instructs Dixie to take Ben's money belt to Judy, then hides from the sheriff and his posse. Morgan and Rocky also go to Judy's ranch and, holding her at gunpoint, demand that she reveal the location of the mine. Judy, who was told the mine's location by Ben, directs Morgan to the site, while Rocky stays behind to guard her and Dixie. Morgan finds Wyatt carrying bags of gold from the mine and kills him. Soon after, a group of Morgan's men ride up and begin collecting Ben's gold. Bob and Chito, meanwhile, arrive at Judy's and, following a brief gunfight with Rocky, rescue her and Dixie and head for the mine. After a fierce fight on a runaway wagon, Bob captures Morgan, while Chito joins the sheriff's posse in a gunfight with Morgan's men. With Morgan and the gang finally arrested, Judy is about to convince Bob to stay at her ranch when a terrified Chito races by on his horse and screams that Dixie has just proposed to him.