Rancher Terry Dugan returns to the town of Brentwood and to his fiancée, Helen Frazer, banker Bob Frazer's daughter. Unknown to them, Bob is being blackmailed by a former business partner, saloon owner Frank Gilmore, into revealing the routes taken by payroll-carrying stagecoaches which Gilmore's men rob. When Johnny Mack, who has been hired by the State Protective League to investigate the robberies, shows up at his Golden Gopher saloon, Gilmore orders his henchman, Lacey, to start a fistfight with him. After Johnny knocks out Lacey, he and his old friend Casoose, whom he has run into in Brentwood, go to see Frazer. Johnny suspects Frazer of being involved in the robberies although Casoose defends his character. Johnny sets up a phony gold shipment in order to trap the gang and succeeds in capturing one of them, Pacos. Frazer is implicated in the robbery as he was the only person Johnny informed about the shipment. Gilmore then orders Frazer to break Pacos out of jail, which he does. After Johnny accuses him of being involved in the robberies, Frazer asks him for twenty-four hours to clean things up and sets a trap for Gilmore, but Johnny intervenes before Frazer can shoot Gilmore. Terry and Helen overhear her father confess to Johnny that years before, when he and Gilmore were partners back East, Gilmore absconded with their clients' money, making it appear that he, Frazer, was the guilty party. Frazer went to prison and when he was released he headed West to make a new start. Although Frazer admits that he has allowed Gilmore to blackmail him to keep his past a secret from Helen and Terry, the eavesdropping Helen and Terry burst in to console and reassure her father. Johnny then devises a plan and the sheriff agrees to assist in trapping Gilmore by locking up Frazer. When Gilmore attempts to shoot Frazer in his cell, Frazer informs him that there is a document detailing Gilmore's activities in his safe and that it will be passed on to the sheriff should anything happen to him. Later, Johnny and Casoose trap Gilmore as he tries to open Frazer's safe, but two of Gilmore's men surprise them. However, Johnny and Casoose escape and Johnny chases after Gilmore and captures him. Later, Frazer informs Johnny and Casoose that Helen and Terry are on their honeymoon and thanks Johnny for his help.