Jack begins his story as his family is heading west with a wagon train. Out of ignorance, they offer a group of Native Americans whiskey. The Native Americans kill and rape several members of the wagon train, then return the next day to offer ponies in recompense for their bad behavior. Because they cannot speak to each other, the pioneers believe the Native Americans have come for 10-year-old Jack Crabb and his older sister Caroline. When Caroline figures out the error, she leaves the Native American village, but Jack stays and learns the ways of the Cheyenne. He eventually earns the name Little Big Man, granted by the village chief, Old Lodge Skins.

Several years later, the Cheyenne have a big get-together where they talk about the problem of the encroaching whites pushing into their territory. They break up and head home, but encounter soldiers on the way. They face off, but the Cheyenne break and run. Jack is caught up in the charge, but convinces a cavalryman he is a white man.

Jack ends up being adopted by a family in western Missouri. He goes to school for a couple of years, eventually leaving when his heart is broken. He earns his living as a guide from St. Louis to Santa Fe, then as a mule driver from Denver to Kansas City. His mule train is ambushed by Cheyenne. He convinces the Cheyenne he is Little Big Man, and he advises Old Lodge Skins to go north to the Powder River, away from the whites. Old Lodge Skins agrees, and Jack returns to Denver.

Jack marries and has a child. He is somewhat successful in business, but his partners cheat him and he is forced to leave town in a hurry. The stage to Kansas City is ambushed by Cheyenne. Jack rides to get help, but returns to find his wife and son missing. He is angered—but perhaps more depressed, and spends some months drunk, until his sister pulls him out of the gutter.

Jack straightens up and joins his sister, hauling freight for the Union Pacific construction of the transcontinental railroad. When he hears that a group of scouts are headed to find the Cheyenne who are harassing the construction, he joins in. A Cheyenne warrior is killed in an isolated grove, where he is protecting a woman giving birth in the woods. Jack assumes responsibility for her, following her back to the village—Old Lodge Skins’ village. He has another child with the woman he discovered, but when soldiers track the Cheyenne down and attack, Jack takes the uniform of a fallen soldier and looks for his Cheyenne wife and child. He is unsuccessful, and heads back to Kansas City.

In Kansas City he meets Wild Bill Hickok, who teaches him how to shoot. He also discovers a niece, a young woman working in a whorehouse. He removes her, sets her up for fine living, and works as a buffalo hunter to make money to send her to school. She succeeds so well, she ends up marrying the son of a senator. Jack ends up on an army ship, headed upriver to supply General Custer as he attempts to root out the Sioux who are on their own land, but messing with the new influx of whites, headed for gold in the Black Hills.

Jack ends up scouting for General Custer, who (as is his habit) is ignoring the advice of his scouts and officers. He ends up on a bluff above the Little Bighorn River, and he is surrounded by Cheyenne. Jack is with them as they are overwhelmed. He is shot, then hit in the head.

He awakens in the Cheyenne village. He has been saved by a Cheyenne whose life he had saved long ago — now they are even.

Old Lodge Skins is very old and blind, and he is now ready to die. Little Big Man walks with Old Lodge Skins to the top of a hill. Old Lodge Skins sings his death song and asks the Everywhere Spirit to watch over his son, Little Big Man. He lies down and dies.

Ralph Snell tells the readers that Jack Crabb died at that point in the story. Ralph has checked Jack’s story, and verified much of it; but he cannot find Jack Crabb’s name anywhere in the records.