Jimmy McClean's blue eyes get him teased and bullied by the kids in school, telling him "You're just an Indian pretending to be white," because he's half-Scottish and half-Lakota, but he's never met another Lakota with blue eyes and light skin like his.
That's when Grandpa Nyles steps in with a cross country tour to introduce his grandson to another blue-eyed Lakota, Tasunke Witko, also known as Crazy Horse, also known as Light Hair when he was younger.
They take a cross-country trip to visit the many places Crazy Horse grew up, lived, and learned, including the place where he fought in the Battle of the Greasy Grass and Battle of the Hundred in the Hands, and finally surrendered to General George Cook, and was later killed by soldiers.
Jimmy sees first-hand how the Long Knives remember his ancestors' history incorrectly, and only from their perspectives, and that Crazy Horse's history is more complex and fraught with sacrifice and difficult decisions than he ever imagined.
Learning about Crazy Horse's sacrifices and battles imbues Jimmy with a sense of pride and confidence he didn't have before. So when Jimmy goes back to school, and his bullies greet him, he stands a little taller with the courage to face his tormentors with confidence.