This one begins after the Civil War when the Overland Telegraph Company is persuaded by rancher Jim Kerrigan to allow his own men to extend the line to Baxter Springs, guaranteeing to pay for the construction himself if it isn't finished at the end of two months. Land promoter Burton Wheelock will lose money if the line is completed and gets ex-rustler Larry Foster, fiancée of Sandra Kerrigan, to sabotage the work. Telegraph company trouble-shooter Johnny Mack, investigating the sabotage, saves Kerrigan's men Joe Farr and Cappy from masked outlaws. Henchman Mugsy is captured by Johnny, while Larry, Slim and the other henchmen escape after shooting telegraph patrolman Nevada. Larry kills Mugsy before he can identify the gang leader. Henchman Straker is captured by Johnny and jailed. Slim steals Johnny's identification card from his saddle bag, and it is found near the jail when Wheelock's men help Straker break jail and kill a deputy sheriff. Because of the card, the Marshal arrests Johnny, but Joe comes to his rescue. An attempt to fire the Kerrigan ranch is foiled, and Larry's hat is found, which proves to Sandra her fiancée's crookness. Larry is trailed to Wheelock's office, and both are killed in a shootout with Johnny, Cappy and Joe.