During the Civil War, livery stable owner Joan Britton learns that Union forces are in desperate need of horses and asks her cook, Heyoka, to help her find the great herds kept by the Sioux. On their way to the Sioux village, Joan and Heyoka are secretly tracked by horse trader Stephen Cook, who wants the valuable horses for himself. At the village, Chief Red Cloud tells Joan that the horses, a gift from the Nez Perce, are sacred and therefore not for sale. After eavesdropping from behind a tree, Cook decides to steal the horses, and returns later with his men. The Indians try unsuccessfully to stop the thieves, and a horse and brave are shot in the skirmish. Physician Jonathan Westgate then arrives in the Sioux village and helps Red Cloud to heal the injured horse. Red Cloud explains that the tribe has elected not to pursue the horse thieves, fearing that the Cavalry might come and appropriate their remaining land. Red Cloud gives Jonathan a horse, and the physician promises to help locate the thieves. In town, Jonathan befriends blacksmith Ahab Jones and soon falls in love with Joan. Explaining that he gave up medicine because he was unable to help many dying Union soldiers, Jonathan sets up shop as the town veterinarian. That day, Cook arrives with three hundred horses, which he claims he bought from another dealer. Jonathan, however, removes an arrowhead from the horse of Cook's foreman and immediately suspects him in the horse theft. Later, Jonathan learns that the local horse ranchers are angry because Cook's men have been intimidating other horsemen attempting to sell to the Cavalry. Jonathan suggests that the ranchers journey to a nearby fort together to explain the situation to Major McKay, but Cook foils this plan by kidnapping Jonathan and persuading the ranchers to return home. When one of the ranchers defies him, Cook has one of his men stab him and places Jonathan's scalpel near the body. Later, while he is being held captive at Cook's ranch, Jonathan performs an operation on Cook, saving his life. As soon as Jonathan is released, the townspeople brand him a murderer and try to hang him. Jonathan escapes and tells Red Cloud that he has seen a stolen Sioux horse at Cook's ranch. After Red Cloud agrees to help clear Jonathan of the murder charge, Cook discovers the doctor's plan and gets rid of the horse. Joan informs Red Cloud of this, but the chief accuses her of setting up the theft of the tribe's horses. The chief takes Joan and Jonathan to an Indian council, where Stand Watie, a Cherokee Confederate general, tries to convince Sioux, Oglala, Nez Perce, Cheyenne, Crow and Blackfoot leaders to join the Southern forces. As he is white, Jonathan is allowed to speak only after surviving a bludgeoning by a group of braves, and he expounds upon the Northern belief that no one is inferior because of skin color. Meanwhile, Cook and his men raid the remaining Sioux herd, killing a child in the process. Horrified, Red Cloud accuses Jonathan of treachery and sends his men to drive away the horse thieves. Hoping for assistance, Cook tells the fort that the Indians have raided a herd of horses that he purchased. After Joan and Jonathan escape from the Sioux village, Jonathan finds Cook and defeats him in a fistfight. Jonathan finally convinces McKay of Cook's guilt, after which the major promises Red Cloud that the Cavalry will punish the murderers and pay for the horses. Satisfied, Red Cloud agrees to maintain the peace. Later, Jonathan enlists in the Union army and promises to marry Joan upon his return. + −