Capt. Demas Harrod and his new recruits join the 3d Regiment of the U. S. Cavalry and find that the ambitious and opportunistic fort commander, General McCabe, is preparing to fight the combined forces of the neighboring Indian tribes. Demas has fallen in love with Lou Woodard, who lives in nearby Mule City. While visiting her one evening, he is interrupted by Sol Rogers, the regiment's chief scout, who plans to marry Lou. The two men fight and become enemies. Demas returns to the fort and is instructed to put his men through a crash training program, after which they celebrate their first leave in Mule City and run into trouble with the town marshal and his henchmen. Demas and Sol then conspire to avenge their men. At an officers' ball on the eve of the campaign, Sol realizes that Lou is in love with Demas, but Lou tells him that Demas seems to have lost interest in her. As the campaign opens, Demas becomes apprehensive when McCabe, disobeying his own orders, splits his forces, sending Demas against a band of Sioux. Demas' men suffer heavy losses, but they manage to retreat when they are joined by Sol. Demas and Sol, attempting to find water for the wounded men, are ambushed and Sol is killed. That night, after the Indians withdraw, Demas leads his reduced force to rejoin the regiment and finds that McCabe and his men, fighting the Indians on their own, have been massacred. He returns to the fort and to Lou.