Dressed as civilians, Lt. Burke and Sgt. Calvin search for Linus Quincannon, a soldier who quit the Army in protest over a brutal Indian massacre and now makes his living as a scout. They have been ordered to bring Quincannon to an Army fort to speak with his former commanding officer, Col. Harry Conover. When Quincannon refuses to go with them, the soldiers arrest him. At the fort, Conover tells Quincannon that a shipment of repeating rifles was stolen from a train during a violent raid by hostile Arapaho Indians, led by Iron Wolf. Because Quincannon has lived among the Indians, Conover wants him to hunt for the missing guns. Quincannon turns him down, but as he is leaving, attractive Maylene Mason arrives. She requests an escort to take her to Fort Smith, where she plans to ransom her brother from the Arapaho, who, she believes, captured him during the rifle robbery. Conover denies her request because he is convinced that the reports listing her brother as dead are correct. Knowing that the Indians have no use for money, Quincannon's suspicions are roused by Maylene's story, and he suddenly changes his mind about the scouting assignment. He is sure that something unlawful is going on at Fort Smith and hopes that Maylene will help him uncover it. He requests that Burke and Calvin, whose persistence he admires, accompany them. As the party advances into Indian country, Quincannon spots a small band of Indians. He and Burke investigate, and when an Indian shoots an arrow at Quincannon, he kills him with a knife. He identifies the dead Indian as an Arapaho and cuts off his braids. Quincannon then helps the others disguise themselves as Indians, and they safely cross through Sioux, Arapaho and Cheyenne territories. At Fort Smith, the party is warmly welcomed by Capt. Bell, who verifies the death of Maylene's brother, adding that Lt. Hostedder was the only survivor of the raid. Quincannon questions Hostedder, whose story seems dubious to him. Later, after conferring with Maylene, Quincannon hides in the barn to see who comes for the ransom that she is supposed to leave there. After capturing Hostedder, Quincannon searches his room and finds $2,000 in gold hidden in an Arapaho bag. He speculates that the money is from a train robbery and was used by the Arapaho to buy information about the gun shipment. Later, Bell kills Hostedder to prevent him from exposing his part in the theft of the guns, but accidentally reveals to Quincannon knowledge of the rifles, which proves that he was involved. Determined to bring Bell to justice, Quincannon, Burke and Calvin set out to find Iron Wolf, the only remaining witness to Bell's betrayal. They first buy whiskey from Blackfoot Sam, a whiskey trader, and learn that a big powwow is being held nearby. Later, on Bell's orders, the three are ambushed leaving camp. After killing all but one of Blackfoot Sam's men, they proceed to the powwow location. Secretly, they observe Iron Wolf's demonstration of the repeating rifles and from his speech, learn the location of the rifles. When they reach the hiding place, Quincannon and Burke get the Indians in the camp drunk on whiskey. Meanwhile, Calvin locates the rifles and uses gunpowder to blow them up. Just then, Iron Wolf appears with a band of Indians and chases the white men. After several gunfights, Quincannon captures Iron Wolf and keeps him prisoner until Bell arrives to arrest Quincannon for the murder of Blackfoot Sam. After Iron Wolf identifies Bell as the man who told him about the rifle shipment, however, Quincannon arrests Bell. Later, Quincannon proposes to Maylene and is reinstated into the Army.