Wild Bill Jones, a cowboy who writes plays, is being harassed by Buck Dawson, Nevada Norton and Pete Sleen, henchmen for cattleman Rance Harris, when "Silver Jim" Donovan rides into the town of Winchester. Jim saves Wild Bill from the three hoodlums, who were trying to force him to use his influence to stop saloon keeper Queenie Canfield from supporting mayor Dr. Thad Morgan for the state senate. To thank Jim, Bill brings him to town to introduce him to Queenie. While they are waiting for her in the saloon, the three henchmen arrive and start a brawl with Jim. When Nancy Lee and her fiancé, incumbent Senator Walter Kincaid, happen to see Sleen about to shoot Jim in the back, Nancy urges Kincaid to save Jim. While thanking Kincaid, Jim tells his new friend of his five-year search for a man with a scar like a lightning bolt on his left arm, the man who shot him in the back with a silver bullet and murdered his father. Kincaid then returns to his office and Harris, his campaign manager, reminds him of their plan to embezzle money from local ranchers. He also points out the fact that Jim is the only person who could reveal their tainted past. Kincaid looks at the lightning bolt scar on his arm and goes to Doc Morgan to ask him to remove it. After surgery, Kincaid notices that Jim has left a drawing of the lightning bolt scar and, realizing that Doc knows the truth, shoots the kindly man. He then convinces Dawson to accuse Jim of killing Doc, but there is not enough evidence to sustain the charge. Queenie then talks Doc's widow, Emily, into taking her husband's place as the reform candidate for the senate, with Jim as her campaign manager. On the day of the election, Bill overhears Kincaid consulting the corrupt Dr. Winslow about his now-infected scar. Winslow says Doc has made the scar worse, and it will never go away. Bill is captured by Kincaid and his men but manages to alert an already-suspicious Nancy to Kincaid's real identity. Dawson chases Nancy but Jim, who is riding by, saves her. She then tells Jim that Kincaid is actually the man with the scar, and they race to town to tell the ranchers. In town, the dance hall girls who work at Queenie's saloon picket with signs proclaiming that any man who does not vote for Emily will no longer by welcome at the saloon. Jim announces Kincaid's true identity, and the furious ranchers trap Kincaid and Harris inside their office. Kincaid allows Harris to be shot, then notices the election poster that proclaims his own courage and decides to face Jim in a shootout. Despite a trick by the senator, Jim beats Kincaid to the draw and kills him. Later, as Emily prepares to become the first woman senator, Jim and Nancy make their wedding plans, and Queenie unsuccessfully tries to convince Bill to make it a double wedding ceremony.