The Mesquiteers—Stony Brooke [John Wayne], Tucson Smith [Ray Corrigan], and Lullaby Joslin [Max Terhune]—reunite with an old friend, Dave Carson [William Farnum], who is prospecting near Santa Fe Junction. They meet Dave's youngest kids, Billy [Martin Spellman] and JulieJane Carson [Genee Hall]. JulieJane is immediately infatuated with Stony Brooke, and Dave's older daughter Nancy [June Martel] has grown into a pretty young woman. Dave shares the news of gold found on his land, but he resists filing a claim because it would alert the town mayor, Gil Byron [LeRoy Mason], whom he does not trust.
After chasing two trespassers from Dave's property, the Mesquiteers catch one, but the other escapes. He reports to the mayor, who now knows Dave has struck gold. The trio attempt to jail the man, but they are told that detention requires a court order signed by Judge Henry J. Hixon [Ferris Taylor]. The judge, compliant with the mayor, lets the farce of a trial proceed, and false testimony from the mayor’s ally leads to fines of $100 for each Mesquiteer.
Seeing how corruption has seeped into town, Stony suggests a petition to appeal to the territorial governor to recall the mayor. As Stony, Dave, and JulieJane ride off on a buckboard to deliver the petition, the judge warns Gil Byron, who responds by sending two henchmen to seize the petition and to file a claim for Dave’s mine in the mayor’s name. The trio recruit Carey and Franklin to sign the petition—Ben Carey [Yakima Canutt] and John Franklin [Nelson McDowell]—and Stony heads to file the claim while Dave and JulieJane head toward Placerburg. A tense chase ensues, and a shot closes in on the buckboard, ending with Dave killed in the crash and JulieJane losing her life beside him.
Now the mayor turns to framing Stony for the murders. US Marshal Jim Wood [Tom London] arrives to arrest him and offers help, while Tucson and Lullaby join in, with Jim deputizing them to watch over Stony. The sheriff arrives to take him, but Jim, Tucson, and Lullaby stand by him. They work to assemble an alibi with Carey and Franklin, but the mayor’s men intercept and fatally wound Carey and Franklin. The trio presses on, while the mob in town grows louder and more menacing.
In the meantime, Tucson and Lullaby are ambushed and held in a shack by two of the mayor’s henchmen, and Billy learns of their disappearance and sets out to rescue them. He succeeds, and Carey and Franklin arrive moments later; the five race back to town to aid Stony. The Marshal fights to keep the mob from breaking into the jail, and he entrusts Nancy with the jail keys, telling her to free Stony. Before she can reach the cell, a rock crashes through the window and knocks Nancy unconscious, and the mob then starts a fire with dynamite aimed at the jail. Stony retrieves the keys from the still-unconscious Nancy and, after the back wall is blown out, escapes with the others.
Tucson and Lullaby corner the mayor, the judge, and several henchmen at gunpoint. The judge, no longer willing to shield Gil Byron, admits he sent a telegraph to the authorities, and the mayor shoots him. A final, brutal fight follows, and the Mesquiteers emerge victorious.
With the danger over, Stony, Tucson, and Lullaby say goodbye to Nancy and Billy, and vow to return soon with machinery to help work the mine. The town has survived the upheaval, and the trio rides off, ready for the next adventure.
