Bordertown is set in the 1880's, and centers around two lawmen, an American Marshal and a Canadian Mounted Policeman, who must share jurisdiction of a small town that straddles the U.S./Canadian border. Both are romantically interested in Marie Dumont, the French widow of the town doctor, who has taken over her late husband's practice.
A barroom fight between an American rancher's son and a Canadian farm boy result in the shooting death of the American. Jack and Clive attempt to take the prisoner to Ft McCloud, but the dead boy's father wants revenge.
A Mountie mail wagon is ambushed and robbed, and the crime is made to look like an Indian attack. Jack and Clive are suspicious, and soon determine that the thieves were Mountie deserters. Meanwhile, Marie's nephew comes to town to visit.
Howling Dog, a young Blackfood, accidentally causes a fire in Marie's store while attempting to steal food. After the Indian is released when Marie refuses to press charges, he is murdered by Erskine, the Canadian Indian Agent. Marie discovers that Erskine has been selling Indian rations to the townspeople for profit.
Jack reluctantly hangs a prisoner, but the prisoner survives the hanging. When Jack refuses to hang him again, the judge sends in a government appointed hangman. Barry Joe's only chance for clemency is if he names his accomplices. The problem is, his throat is so badly damaged that he can't speak.
A Chinese immigrant overhears a plot to rob a gold shipment. Determined to be a good citizen, he informs the law the plot, but is fearful for the life of his fiancee, who is arriving on the stagecoach.
While investigating the presence of a band of Cree Indians camped near the town, Jack and Clive discover that a white boy is living among them. The boy's uncle is determined to get him back, even if it means endangering the town by starting a war with the Indians.
Charles Ashley intends to bring a railroad to Bordertown, but Jack is incensed when the railroader turns out to be a former Confederate Captain from the Civil War who abandoned his wounded men -- including Jack -- to the enemy. When the two men exchange shots, Ashley gets rid of his gun, and claims that he was ambushed by Jack.
The lawmen are troubled when an aging gunfighter comes to Bordertown, followed by glory-seekers who are out to kill him, and a novelist, who wants to write a story about him.
Liam becomes infatuated with a blind gypsy fortune teller who is being forced by her employer to convince men that their future includes earning a fortune in a new business venture, so he can sell them stock in a non-existent silver mine.
A young easterner challenges his employer to a gunfight after he is cheated out of part of his wages. Jack attempts to teach the young man to shoot.
Two outlaw brothers, believed to be dead, come to Bordertown to rob the bank. Before they can carry out their plan, they are recognized by Hiram. When he speaks up, he is fatally struck by one of them. The brothers leave an accomplice behind so that they can escape, and when he tries to rejoin them, they shoot him. Knowing that the brothers will return, Clive and Jack set a trap to capture them.