A cowboy's love for a Chinese slave girl triggers controversy in a Western town.

In San Francisco in the 1870s, freight line operator Linc Bartlett is shocked when he sees a lovely, nineteen-year-old Chinese girl, Kim Sung, being sold at a slave market. Linc buys her, intending to set her free, but Kim has nowhere to go so he is forced to prepare to take her to his home in the mining town of Jericho. Cheng Lu, a young Chinese immigrant who speaks perfect English, taught to him by American missionaries, asks Linc to take him to Jericho to join his uncle Wu, who runs a laundry business there. Almost immediately the two men clash, Linc because he feels that the Chinese are an inferior race, and Cheng because he resents his countrymen having to grovel in front of white men. On the journey to Jericho, Kim assumes that she is required to have sex with Linc, but he rejects her and warns Cheng, who has offered to buy Kim from him as a slave, to stay away from her. After Linc threatens to cut off Cheng's queue, or pigtail, his symbol of cultural identity, Cheng warns Linc that he will have to kill him first. In Jericho, Linc's mother initially rejects Kim as a heathen, but later softens, teaches her some English words and helps her to adjust to her new surroundings. After Linc rescues Cheng from being harassed by several cowboys, Linc takes him to his uncle Wu's premises, where Cheng is dismayed when Wu advises him to be subservient and to speak pidgin English in order to survive. Later, in a gambling hall run by Lili Raide, Linc's former sweetheart who is half Indian and half French, Cheng wins one thousand dollars in a game of chance of his devising, involving cockroaches. After Cheng offers the cash to Linc in exchange for Kim, Linc throws him out of the hall. Intending to challenge Linc, Cheng hires a Scripture-quoting gunfighter known as The Deacon to teach him how to become a fast draw. After Cheng tells Kim, who is helping Linc's mother in the house, that she is becoming contaminated by the Americans and asks her to leave with him, she replies that she honors her "master" and his mother and refuses to go with Cheng. When Mrs. Bartlett insists that Kim and Linc accompany her to an Easter church service, the townspeople are shocked, although the minister welcomes them. Later, after Kim tells Linc about her past life and they realize that they are in love, Kim shocks Linc's mother by telling her she wants to have his children. Mrs. Bartlett tells Kim that she cannot have children unless she is legally married. The townspeople refuse to accept Kim as an equal and, afraid of Linc's prowess with a gun, strike at him economically, destroying his business. After Linc fails to "westernize" Kim, he is forced to accept her for who she is and asks her to marry him. They receive Mrs. Bartlett's blessing. When Cheng, in a gesture of reconciliation, offers Linc a loan to help save his business, Linc throws him out of his office. Cheng has become a proficient gunman under The Deacon's reluctant tutelage and when he enters the gambling hall wearing guns, The Deacon attempts to humiliate him. In a fair shootout, Cheng kills The Deacon. Cheng then tells Linc that he has caused him to lose face. Although Linc apologizes, Cheng states that he intends to kill him, suspecting that Linc is afraid of him because he has outgunned his teacher. Linc then reveals that it was he who taught The Deacon. As the men prepare to fight, Kim reaffirms her love for Linc and tells him that perhaps one day they could be allowed to be happy together, but not in their lifetime. The two men are about to draw their guns when Kim, who now realizes that not all women are slaves and therefore have a freedom of choice, steps between them. When Cheng moves away and draws his gun, Linc shoots him in the hand. After Kim pleads with Cheng to take her back to her people, he reveals that he has changed his views on the views of women and tells Kim that he wants her not as a slave, but as a wife. As proof of his genuine love for her, Cheng asks Kim to cut off his pigtail, symbolizing his revolt against the ancient customs of servitude. Linc reiterates his love for Kim and his wish to marry her, and states that he will not interfere in her decision. Kim hesitates, then chooses Cheng and they walk off together.