Written by A. B. Guthrie Jr. in 1947, The Big Sky is an adventure novel set on the Western frontier. It tells the story of seventeen-year-old Boone Caudill—who, at the beginning of the novel, is living with his family in Kentucky. Boone’s father is a bully who physically abuses Boone, his brother, and their mother. One evening, as Boone is being beaten, Boone hits his father on the head. Knowing that his father is seriously injured, maybe even dead, Boone steals his father’s rifle and runs away from home.

Boone’s maternal uncle, Zeb Calloway, lives an “uncivilized” life in the mountains, and Boone resolves to follow in his footsteps and heads West. While walking, he meets Jim Deakins. Jim has a mule and a cart, and he takes Boone to Louisville. Jim, unhappy with his life, decides to join Boone.

Boone and Jim are recruited onto the Mandan, a French keelboat traveling up the Missouri River. Also on the boat is Teal Eye, a twelve-year-old Native American who has been kidnapped by a rival Indian tribe. Boone falls in love with her at first sight, but she disappears when the boat reaches Blackfoot country. Not long after, the boat is attacked by a Native American tribe, and the only survivors are Boone, Jim, and hunter and guide Dick Summers.

The three men survive by hunting and trapping, and Boone falls in love with the outdoor life. However, Dick, deciding he is too old for the life of a mountain man, returns to a farming life in Missouri. Boone wants to find Teal Eye, and he and Jim enter Indian territory, where they find many have been killed by smallpox. Teal Eye has survived, however, and she becomes Boone’s wife. Boone and Jim embrace the tribe’s way of life and continue to live among them.

Later, Teal Eye becomes pregnant and soon gives birth to a son. To Boone’s disappointment, the son is blind and has red hair. Boone thinks that Teal Eye has cheated on him with Jim, as Jim also has red hair. Boone proceeds to shoot and kill his closest friend and, leaving Teal Eye, flees to his home state of Kentucky. When he returns home, his mother reveals that though their immediate family does not have red hair, red hair does run in their family, filling Boone with regret and guilt over his unjust, violent actions.

Unable to settle back into a “civilized” life in Kentucky, Boone leaves once again and visits Dick Summers in Missouri. He tells him what he did to Jim and Teal Eye: “This here hand done it. . . . I kilt Jim.” Unwilling to spend the night with Dick, Boone leaves.