Capt. Kern Shafter of the U.S. Cavalry is stripped of his rank and humiliated before his men for assaulting Capt. Edward Garnett with a saber. Kern, who had assaulted Garnett to avenge the honor of his fiancée, becomes a card-playing drifter and several years later journeys to the Dakota Territory to begin a new life. On the train, he meets the beautiful Josephine Russell, whom he protects from a roughneck, and although he admires her, the two say goodbye upon reaching Bismarck. Kern joins the Seventh Cavalry at Fort Abraham Lincoln, where he encounters his old comrade, Capt. Myles Moylan, who immediately promotes Kern to the rank of sergeant. Kern is far less pleased to discover that Garnett is also stationed there. Garnett threatens to break Kern unless he leaves the fort, but he insists on remaining. Kern does make one new friend, Pvt. Donovan, a feisty but amiable Irish-American soldier who respects Kern for defeating him in a fistfight. When several miners are murdered by Indians, Garnett, accompanied by a large detachment of men, confronts Chief Red Owl and his warriors on the Sioux reservation. Despite the chief's protests, Garnett sends Kern to arrest the guilty Indians, and just as the incident is about to erupt into a battle, an additional company from the fort appears on a nearby hilltop, and Red Owl agrees to give up the murderers. The Army scout is visibly relieved. The Sioux, he explains, have been pushed back too far and "won't be pushed any further." One evening Kern accompanies Josephine to her home where, to his distress, he learns that Garnett has also been courting her. Josephine later admits that while she likes Garnett, she also is intrigued by Kern, who she assumes is running away from some dark event in his past. Kern and Josephine kiss, but he refuses to explain the cause of his enmity with Garnett. Moylan, who knows the reason, realizes that by continually giving Kern dangerous assignments, Garnett is trying to get his old enemy killed. Without informing Kern, Moylan sends word to Washington that he has additional information regarding Kern's case. Meanwhile, Garnett sends Kern and several of his men into dangerous territory, and only by using his wits is the sergeant able to save his men from being massacred by a party of attacking Sioux. Later, Kern visits the Carson farm, where Josephine and Garnett are, like himself, seeking shelter from a storm. Exasperated by Kern's hostility toward Garnett, she asks the men to settle their differences while she cooks dinner. Garnett reminds Kern of his illicit rendezvous years earlier with Alice, then Kern's fiancée, and asserts that he has no intention of withdrawing his attentions to Josephine. Kern knocks Garnett to the floor, which so angers Josephine that she sends Kern away. Soon after, however, as the soldiers ride out with General George Armstrong Custer to fight the Sioux, she gives Kern her good luck pin. Garnett sends Kern and Donovan into a trap, and they are surrounded by attacking Indians. Mortally wounded, Donovan orders Kern to escape while he provides cover. Donovan sings an Irish ballad and shoots Indians until he finally succumbs, and Kern returns to camp on foot. Eager for revenge, he insists on joining Garnett in battle, but as he rides toward the captain's position, he witnesses the massacre of Custer and his men at Little Big Horn. After sending out a request for help, Kern rides off to join Garnett's men in battle. As he approaches, Garnett shoots at him and the two men fight. Garnett is about to finish Kern when he is himself killed by a Sioux bullet. Kern then joins Moylan in battle and is seriously injured. Later, while recuperating in the hospital, Kern learns that because of Moylan's intervention, his original rank of captain has been restored. Josephine then visits him and the two kiss.
