In Texas after the Civil War, Ivy Preston delivers a shipment of guns to her fiancé, Alan Sanford, who then leaves to raise an army with Mexican Emperor Maximilian and resume the fight against the Yankees. When Kirk Jordan, a Southerner who believes in the peaceful co-existence of the North and South, rescues Ivy from arrest by Major Isaiah Middlebrack, the entire town joins in the fight. Back at her poverty-stricken ranch, Ivy, her "Granna" and foreman Chuckawalla are confronted again by Middlebrack, who has brought with him the cavalry, led by Lieutenant David Nichols. Middlebrack slyly agrees not to arrest Ivy. Instead, he intends to tax all of her 10,000 head of cattle, and accepts land scrip for their ranch as payment. Determined to outsmart the major, Granna gets Middlebrack drunk, while Ivy mobilizes her ranch hands with the help of Kirk and his fur-trapping sidekick, Cal Tuttle. Later that night, Ivy, Kirk and Cal head the herd toward the Rio Grande River. After Granna and Chuckawalla catch up, they evade the cavalry by crossing the river. At Kirk's suggestion, a reluctant Ivy agrees to herd the cattle on a dangerous trek up to Abilene, Kansas, where she will be able to sell the cattle at a high price due to the introduction of the railroad. Middlebrack goes to the state capital and receives the authority to arrest Ivy and her troupe for tax evasion and treason, and the cavalry follows in pursuit. After the herd endures a blizzard and Granna fights illness, Alan arrives exhausted at the campsite and informs them that his plans to build a rebel army were destroyed when the emperor was dethroned and executed. When Ivy and Alan announce their engagement, there is a celebration, but Kirk is disappointed. Confronted by Comanches, who ask for one steer in exchange for peaceable passage through their land, Alan refuses their request despite Kirk's advice. After a dust storm, the herd is attacked by Comanches, who retreat when the cavalry approaches. Middlebrack arrests everyone and takes command of the wagon train, but Kirk and Cal manage to slip away unnoticed. They follow the herd for three days, but ride to the rescue when Comanches set the grasses on fire around the herd. Cal kills Middlebrack, and after the dust is settled, Lieutenant Nichols honors the death of a ranch hand and escorts the herd to the Kansas border. On arrival at Abilene, Alan disappears and the Preston herd saves the town from losing the railroad's business. Kirk confesses his love to Ivy and says goodbye. When Ivy discovers Alan is helping to form the Ku Klux Klan, she realizes the error of his ways and runs after Kirk, catching up with him in time to join Cal and him on a beaver-trapping trip.