The Big Sky, by A.B. Guthrie, is an adventure novel about the days on the Western frontier. This is the story of Boone Caudill who grows up with a mean and domineering father who he comes to hate. The seventeen-year-old boy decides he is not taking another beating from Pap, knocks him out, and runs away from home.

On the road Boone meets Jim Deakins and rides to Louisville with him. This is the beginning of a long friendship between the two men that ends in a misunderstanding many years later. Boone has an uncle, Zeb Calloway, on his mother's side who is a trapper on the frontier. Boone decides to go West and Jim decides to go with him. The two men sign on to the Mandan, a boat operated by Jourdonnais and Summers and go up the Missouri River into Indian country hoping to make their fortunes hunting and trading in furs. With them is a twelve-year-old Blackfoot Indian squaw named Teal Eye who was kidnapped from her people by a rival Indian tribe. Her father is the Blackfoot chief, Heavy Otter, and Jourdonnais thinks that by returning her, he will be able to do a lucrative business with the Blackfoot. The girl escapes and the Mandan is attacked by another Indian tribe and all aboard are killed. The only survivors are Boone, Jim Deakins and Dick Summers.

The three men live by hunting and trapping in Indian territory. Boone comes to love the outdoor life and his life hunting and trapping. He isn't interested in getting rich, just in having what he needs to survive. When Dick leaves the group, Boone decides he wants to find Teal Eye. He has no idea what happened to her, but they begin to look for Heavy Otter and the Blackfoot. They push further and further into Indian territory and can't find them. Many of the Indians were wiped out in a smallpox epidemic, but Teal Eye survived. Boone follows the Indian custom in asking for her and she becomes his squaw.

Boone adopts the Indian ways and customs and is very happy with Teal Eye. After many years, she gives him a son, but the child is blind and has red hair, like Jim. The distraught Boone shoots Jim, leaves Teal Eye and returns to Kentucky where he finds his brother's son has red hair. After all the years of living outdoors and with the Indians, Boone doesn't fit in with his family in Kentucky. He can't stand the confines of a house. When a friend of the family tries to pressure him into marriage, he leaves. He visits Dick Summers and tells him some of what happened. Can he go back to Teal Eye and the frontier?

This book is an interesting adventure story about the life of the trappers during the periods of America's westward expansion. The book is about life in the wilderness and how people survived.