Cappy is a thirteen-year-old Chippewa boy and Joe's best friend. After Cappy’s mother’s death, he and his brother Randall were raised by their father Doe Lafournais. Cappy is handsome, charming, and an extremely loyal friend. He and Joe have a deep love for one another, and their friendship is notably intimate: they share shoes, talk about everything, and Joe even calls out Cappy’s name in his sleep. Cappy offers Joe support as he copes with Geraldine's trauma and he later helps Joe kill Linden Lark in retribution, despite Joe's protests that he wants to kill Linden alone so that Cappy won’t be legally accountable. However, Cappy saves Joe’s life by tailing him and delivering the shot that kills Linden when Joe is unable to do so. Over the course of the book, Cappy falls in love with Zelia, a Mexican American girl who comes to the reservation on a mission trip. Through her, Cappy becomes more religious. Cappy explores his adolescent sexuality with Zelia, and once she moves back to Montana, the young couple begins exchanging letters. After Lark’s death, Cappy dies in a drunk driving accident while in the car with Joe, Angus, and Zack on the way to see Zelia. Cappy’s loyalty and devotion to Joe are a formidable model of friendship in the book, and his death is a tragedy of adolescence that clearly still haunts Joe even years later.