Stony Brooke, one of the Three Mesquiteers, returns home after an absence of many years, not knowing that his father, Sheriff Brooke, has been murdered and that his boyhood friend and fellow Mesquiteer, Tucson Smith, has been accused of the crime. The real murderer is Blackton, one of the sheriff's deputies, who feared that Brooke was about to expose his undercover activities as leader of a band of outlaws. After Brooke's death, Blackton takes over as sheriff, and on the day that Tucson is to hang, Marsden, his rancher friend, incites a brawl and helps Tucson escape. Homeward bound, Stony encounters the wounded Tucson and helps his friend to the ranch house, where Tucson's sister Helen tends to his wounds. When Blackton and his men arrive at the ranch, Tucson escapes through a trap door, but Blackton tells Stony that his friend killed his father and recruits Stony as a deputy. Believing Blackton's accusations, Stony follows Helen to Tucson's hideout, where Tucson proclaims his innocence and accuses Blackton of the crime. After Stony refuses to believe his friend, Helen helps her brother escape and tells Stony that the circuit judge will exonerate Tucson at his court hearing. When the judge is killed before the hearing, Stony becomes convinced of Tucson's innocence, but continues to work as Blackton's deputy while conducting his own investigation. Stony asks his friend Lullaby, a jack-of-all-trades who has taken over the barber shop, to try to extract confidences from his talkative customers. Lullaby learns that Tucson is headed for Marsden's ranch and foolishly discloses this information to Blackton, who plans to waylay Tucson. Learning that Blackton has set an ambush for Tucson, Stony pretends to shoot Tucson and then lets him escape. Stony then rallies the ranchers to lay a trap for Blackton. The ranchers tell Blackton that they are sending a herd of cattle through the pass and he is to accompany them for protection. Blackton sends one of his men to warn the raiders, but Stony captures him, and as a result, Blackton's men start shooting at their boss, thinking that he is one of the raiders. Realizing that he will be killed unless he can stop his raiders, Blackton confesses, and in the ensuing shootout, Blackton is killed and his men surrender. With Tucson exonerated, the Three Mesquiteers are reunited and head for Texas.