The book follows fourteen-year-old Arnold Spirit Jr., also known as "Junior," living with his family on the Spokane Indian Reservation near Wellpinit, Washington. The book is an epistolary and chronicles Junior's life from the start of the school year to the beginning of summer. It includes both Junior's written record of his life and his cartoon drawings, some of them comically commenting on his situations, and others more seriously depicting important people in his life.
Born with hydrocephalus, Junior is small for his age and suffers from seizures, poor eyesight, stuttering, and a lisp, making him a frequent bullying target for others on the reservation. Junior's only friend is Rowdy, who is abused at home. Despite his reputation as a bully on the reservation, Rowdy often stands up for Junior and they bond over their shared love of comics. Junior's family is extremely poor and has limited access to opportunities. When Junior's dog Oscar gets heat stroke, his father must put him down by shooting him as they cannot afford a veterinarian.
On the first day of school, Junior discovers his mother's name written in his textbook and realizes how old the book must be. Angered and saddened that the reservation is so poor it cannot afford new textbooks, Junior violently throws the book, inadvertently hitting his teacher, Mr. P, and breaking his nose. While visiting Junior at home, Mr. P convinces him to transfer to another high school, sensing a degree of precociousness in him. Junior elects to attend Reardan, a school in a much wealthier neighborhood with no other Indian students.[2] Despite his family's financial situation, they do what they can to make it possible for him to attend. Rowdy, however, is upset by Junior's decision to transfer, and they gradually begin to cease contact.
Junior develops a crush on popular girl Penelope and starts befriending the straight-A student Gordy. His interactions with the white students give him more perspective on both white culture and his own, and he finds himself torn between pressures to fit in at Reardan and his sense of loyalty to his Indian heritage. He realizes how much stronger his family ties are than those of his white classmates, noticing that many of the white fathers never attend school events. Junior also realizes that the white students have different rules than those he grew up with, evident when he reacts to an insult from the school's star athlete, Roger, by punching him in the face, as would be expected of him on the reservation. To his surprise, Roger never seeks revenge, and in fact only ends up respecting Junior more after the incident. Junior also grows closer to Penelope, which soars his popularity as the ‘almost boyfriend’ of the most popular girl in the school.
Roger suggests that Junior should try out for the basketball team. To Junior's surprise, he makes the varsity team, which pits him against his former school, Wellpinit, and Rowdy, who is Wellpinit's star freshman. When Junior enters the court for his first match, his former schoolmates boo and insult him. Junior suffers some injuries from the game, namely from Rowdy knocking him unconscious, but his coach commends his commitment to the team.
Later on, Junior's grandmother is hit and killed by a drunk driver. After her funeral, a family friend, Eugene, is shot in the face by his friend Bobby while both are intoxicated and fighting over the last sip of alcohol. Later, Reardan wins their second match against Wellpinit. Junior feels triumphant until he sees the look of defeat on the Wellpinit players' faces and remembers the lack of hope he had for his future while growing up on the reservation. Ashamed, he runs to the locker room, vomits, and breaks down sobbing. Later, Junior receives news that his sister and her husband were killed in a fire at their trailer.
The tragedies that afflict Junior and his family, though forcing him to question his future and ponder the darker aspects of reservation culture, reaffirm his love for his family and friends, and he eventually learns to identify as both Indian and American. Rowdy later realizes that Junior is the only nomad on the reservation, which makes him more of a "traditional" Indian than anyone else there. In the end, Junior and Rowdy reconcile while playing basketball and resolve to correspond no matter where the future takes them.
