Former army Captain Linus Quincannon makes his living as a scout after quitting the army. Quincannon, who is part-Indian, quit the army after a massacre of natives by the 7th Cavalry. Nevertheless, his former commanding officer, Col. Harry Conover, sends for him. He needs his help in tracing and retrieving 800 stolen Henry repeating rifles and 10,000 rounds of ammunition that were captured by the Indians. The colonel informs Quincannon that Indians had inside information about the real contents of the supply transport. The transport was disguised to look as an ordinary supply run but the Indians knew what was in the barrels. The rifles were en route to Fort Smith where Capt. Bell is in charge. Quincannon is also told that an army payroll was taken. Having lived among natives, Quincannon knows they have no use for money. This suggests that someone at Fort Smith might be involved. The colonel asks Quincannon to go there and investigate the matter and possibly retrieve the stolen rifles from the Indians. At the same time, attractive Maylene Mason arrives and asks to see the colonel. She wants to know whether her brother, serving as trooper at Fort Smith, was killed during a patrol. The colonel confirms it but Maylene insists to go to Fort Smith to see for herself. She claims someone there demanded a cash ransom in exchange for her brother who is a hostage of the Indians. The colonel asks Quincannon to take the lady and two assisting officers with him to Fort Smith. He also gives him a letter of authority over all military commands under his jurisdiction. Dressed in civilian clothing, the group sets out for Fort Smith. But to get there it must pass through dangerous Sioux, Arapaho and Cheyenne territories.