In 1875, a peace treaty between the United States and the Sioux Nation brings calm to the Black Hills of the Dakota Territory. However, a rumor about gold in the hills starts a gold-rush. Many settlers and prospectors invade the Black Hills in violation of the peace treaty. The Army tries its best to keep the gold-rushers out of the Sioux lands in order to avoid renewed confrontations between the Sioux and the Whites. A small fort with a small garrison is entrusted with policing the region. Captain Webb Calhoun is especially strict about keeping the gold seekers out of the Indian lands. This earns him the enmity of the settlers and the gold-rushers. Often times, Calhoun's men get into fist fights with the prospectors in the local saloon. The saloon owner, Ira Jordan, encourages gold-digging on Sioux lands. He figures that sooner or later, the Sioux will attack the train wagons carrying settlers and gold-rushers and trigger a new war between the Sioux and the USA. With the Sioux killed, the Black Hills could become land for the settlers and gold-rushers. Captain Calhoun figures out Jordan's plan and tries his best to prevent it. But the new fort commander, Lieutenant Colonel Lloyd Unger, who rose from the ranks, is gullible and dislikes Indians. Therefore, he is receptive to Jordan's suggestions that the Sioux should be killed because they harass innocent settlers and murder farmers. The gullible commander also dislikes Captain Calhoun since the days when he was a simple sergeant under Calhoun, who is a West Point graduate. Moreover, the two are romantic rivals trying to woo the same girl, Lia Wilson. Crooked saloon owner Ira Jordan convinces the fort commander that Sioux war parties are raiding white settlements and the colonel falls for the ploy. He orders a sortie in force, with all his troops, to the Black Hills to punish the Indians. Captain Calhoun and his small detachment are left to defend the fort. The Sioux, led by Chief Pactola, attack the fort while another Sioux war party ambushes colonel Unger's Cavalry unit in the Black Hills. Calhoun is also responsible for the lives of all settlers, farmers and civilians who took refuge in the fort before the Indian attack and a train wagon that arrived at the fort during the attack.