When his pal, Sam Beekman, captures an Indian sneaking near their wagon train, scout Kirby Randolph, realizing the brave is a follower of Satank, the fierce Kiowa chief, lets him go, then devises a plan to get through the treacherous Cottonwood Draw. He sends the wagons through the night to Laird's Way Station, on the other end of the pass, and goes with Sam to meet Satank and trade some old, useless guns for a promise that Satank will not attack the wagons. Kirby is suspicious that Satank has such a small party of Indians with him, and when he and Sam reach Laird's Way Station, they are horrified to learn that the main force of Satank's braves attacked the wagon train and killed all the settlers. Kirby and Sam are accused of collaborating with the Indians for money and ostracized when they try to get work in another town. Sam learns of an express freight outfit heading for Santa Fe looking for a scout. The owner, Jess Griswold, says that every man is entitled to one mistake and hires Kirby and Sam. Kirby, a self-avowed Indian hater, slugs wagon boss Tuss McLawery, whose mother was a Dakota Sioux, when McLawery taunts him about the massacre. When Kirby finds Ptewaquin, an old Indian woman, driving the wagon of Aurelie St. Clair from New Orleans, he orders the woman off, but Aurelie adamantly states that Ptewaquin goes wherever she goes. Learning that Aurelie has made a deal with Jess to transport rifles to sell to the Mexican army, Kirby warns that Satank will try to capture them. Seeing the tension between Kirby and Aurelie, Jess informs Kirby that he intends to marry her. Along the trail, Kirby's quick thinking saves the wagons from a herd of stampeding horses. During the encounter, Aurelie's dress catches fire, and Kirby rolls her in the dirt and pats her down to put it out. At night, Aurelie tells Kirby about being ostracized growing up because of her no-good father and that she feels this is her one chance to make enough money to be somebody. Ptewaquin soon detects that Aurelie is falling in love with Kirby and warns that he would hate her if he learned that her mother was a squaw. One night, as Kirby is on guard duty, Aurelie playfully approaches him with a knife to his back. He wrestles her into his tent and angrily tell her never to sneak up on a man like a "dirty, thieving Indian." As they lie in each other's arms, she tries to tell him her secret, but they end up kissing passionately instead. While they continue their lovemaking, Tuss hears a Kiowa bird call and runs off into the woods. Jess sees Tuss run off, and sends his assistant Chavez to follow. Jess then sees Kirby and Aurelie exit the tent from opposite sides. The next day, Jess announces that there is a traitor in camp. He shoots and kills Tuss after giving him the chance to shoot first and reveals that Chavez overheard Tuss make an arrangement for Satank to steal the rifles as they cross the river. Kirby devises a counterplan, and during the subsequent battle, Kirby partially scalps Satank before he is shot in the shoulder with an arrow. Kirby gets drunk to blunt the pain as Ptewaquin cuts the arrow from his shoulder. Afterward, in front of Jess, he kisses Aurelie, but later, Jess tells him that she is a "breed," whose mother was the daughter of a Kiowa chief. Jess taunts him by relating Kiowa customs he will have to follow if they marry. As they travel, Kirby avoids Aurelie. When Aurelie gives Kirby a good luck charm she made from the arrowhead he stopped and a knot of Satank's hair, he says he does not want to marry a half-breed and throws the charm in the fire. Jess comforts her, and when he proposes, she says she will let him know her decision before they get to Santa Fe. Chavez convinces Jess that Aurelie will never marry him while Kirby is alive, so they plan to make a deal with Satank for Kirby's scalp in return for safe passage. Jess sends Kirby ahead to scout for water, and he is captured by Satank, who then decides he also wants the rifles and Aurelie. Meanwhile, Jess leaves Sam in charge of the wagons while he takes the pack animals, Aurelie and Ptewaquin through a pass in the mountains, planning to send water back. While Satank goes after the wagons, Kirby escapes and warns Jess. Jess is about to shoot Kirby, but Aurelie stops him. They fight rolling down a hill, and Jess breaks his leg. Kirby, Aurelie and Ptewaquin carry Jess to the horses, but Jess maneuvers away from them, grabs a rifle, and orders them to leave him, saying they will never make it with him along. After they ride off, the Indians attack and kill Jess. As the whites outmaneuver the Indians by splitting trails, Kirby reconciles with Aurelie. Satank approaches with his braves from the rocks above, but Sam, who has learned about Satank's attack, appears in the distance. Kirby, Aurelie and Ptewaquin lead the Kiowa into a trap, and the Indians are routed by Sam and the others. As Satank is about to kill Sam, Kirby rescues him. Satank then tries to stab Kirby, but Ptewaquin stabs and kills the Kiowa chief. Ptewaquin is shot in the back with an arrow, and she dies in Aurelie's arms. Looking at Kirby, she speaks words in the Kiowa language, and after she dies, Aurelie tells Kirby that she said he shall be her daughter's husband. She then reveals that Ptewaquin was her mother. Later in Mexico, Sam sees that Kirby has tied his pony in front of Aurelie's tepee. According to the Kiowa custom, as soon as she finishes feeding the pony, she and Kirby will be married. As the lovers are about to go into the tepee, Sam asks them to make the marriage legal and brings a padre. As the ceremony is about to begin, Kirby and Aurelie kiss.