At the Bar B Ranch, new owner Gene Autry is angry when he discovers that nearby Indians are grazing sheep on his land. He sets out to complain to Chief Long Arrow, but when he arrives on the reservation, he learns that One Mary, the chief's aging relative, is very ill. Concerned, Gene brings her to the trading post and summons a doctor. At the trading post, Gene stops the proprietor, "Smiley" Martin, from cheating Lakohna, an Indian. Then, over Martin's objections, Gene brings One Mary into the post to wait for the doctor. When Nan Palmer, the doctor, arrives, she determines that One Mary is suffering from malnutrition. Gene is shocked by the news and decides to allow the Indians to continue grazing their herds on his land. From Long Arrow's grandson Rona, Gene learns that the Indians do not get enough to eat. Later, Gene encounters Nan at the schoolhouse and helps her inoculate the children. As a favor to Nan, Gene brings medicine to Broken Arm at the reservation. There, he tries to stop some men claiming to be government agents from taking Broken Arm's sheep away from him, but they manage to drive the sheep over a cliff to their deaths. Later, the men are revealed to be cohorts of Martin, who are trying to force Broken Arm's wife Lucy to sell a priceless blanket, but Henderson, the head of the Indian Bureau, refuses to jail them unless he has solid proof that they are harming the Indians. Gene asks Bob Collins, a reporter, to write an expose for the paper, but Bob is not interested in the story. Then Gene telephones Congressman Lawrence, who asks Gene to write a full report. Gene learns that the Indians have lost many sheep, and that they have no water on the reservation with which to irrigate their corn. Without sheep for wool, the Indians are unable to weave the blankets that they sell for money to buy supplies. Thus, Martin is able to cheat them out of their possessions and sell them to curio dealer Fred Bradley. One of his partners covets the necklace that belongs to Long Arrow. Because he knows that the necklace is the property of the tribe, and that Long Arrow would never sell it, Martin decides to kill him, steal the necklace and pin the murder on Lakohna. After Long Arrow is discovered fatally wounded, Gene advises Lakohna to hide until he can discover the identity of the real murderer. That night, Gene and Lakohna sneak into the trading post looking for proof that Martin was behind the attack on Long Arrow. They are discovered and chased by Martin and his confederates. In the morning, Gene and Lakohna are trapped in the rocks, but are saved by the arrival of more Indians. Shortly after, the sheriff arrives with a posse, and Martin is arrested, after which the necklace is returned to Lakohna, who is now the tribe's chief. Bob writes the story, and the resulting publicity causes many people to send gifts to the Indians, and Congress grants the tribe an appropriation. Later, Nan, whose real name is Nanusha, reveals that she is half-Indian and will marry Lakohna.