When Cheyenne Indians threaten to disrupt construction of a railroad through Colorado territory they believe is theirs, Lt. Col. Kilrain of the U.S. Cavalry summons Miles Archer, a Civil War veteran and an expert on the region, to Fort Bellows to organize a special protective guard troop. Archer arrives at the fort only to discover that in addition to the troop, he is also expected to join Sgt. Baker in the rescue of two white women abducted by the Cheyenne five years earlier. Archer initially rejects Kilrain's request, but when he learns that the women, Anne and Jennie McKeever, are the sisters of Johnny McKeever, an old pal of his, he changes his mind. A fighting regiment is then assembled from a group of men who have committed minor offenses at the fort. Among the recruits are Cullen, an inventor; Poinsett, a Southern aristocrat; Ryan, a philanderer; and Grover Johnson, an artist from the East. Before the regiment leaves the fort, a fistfight erupts between Ryan and Baker, who becomes enraged when he finds his wife kissing Ryan. Heading into Cheyenne territory, Archer and his men come across an ailing old Arapaho man, who, before dying, throws his ax at one of the soldiers, hitting him squarely in the back. The men continue on, undaunted, and eventually find the Indian village at which Anne and Jennie are located. It is only after the two sisters are safely brought out of the Indian village that Archer and the others discover that Jennie has become a Cheyenne, and that she is engaged to marry Chief Thunder Hawk. While Anne willingly agrees to return to Fort Bellows, Jennie must be gagged and taken by force. En route to the fort, Archer loses nearly half of his party to Cheyenne attacks and, at one point, discovers that Jennie is secretly signaling the Indians, giving them their exact location. The party finally reaches Fort Bellows only to discover that the fort has been ransacked and that all but one of the men there, a man named Griffin, have been massacred. Griffin tells Archer that the women, including Archer's wife, were sent to Fort Darby. When Archer learns that Fort Darby is the nearest place to get food and water, he decides to lead his party on a four-day journey there. Once again, Archer's party comes under Cheyenne attack and is forced to take shelter on a river island, where a romance between Archer and Anne flourishes. Realizing the danger they are in, Archer sends Baker and Ryan ahead to Fort Darby to get reinforcements. Although Ryan is killed in an Indian ambush, Baker manages to get through to the fort. Back at the river island, the Indian attacks grow in ferocity and result in a full-scale battle. Shortly after Chief Thunder Hawk is killed, reinforcements from Fort Darby arrive, and with their help, the Indians are driven off. Jennie's body, shot up with arrows, is later found next to Chief Thunder Hawk's. With his mission accomplished, Archer professes his love for Anne and asks her to marry him.
