Mattie begins as a recognizable teenager — lazy, ambitious, resentful of authority — and ends as an adult in all but age. Anderson traces her transformation through action rather than reflection: Mattie does not decide to grow up; she grows up because the alternative is death. Her immunity after surviving the fever gives her a paradoxical freedom that drives the novel's second half. She is one of young adult literature's most convincing coming-of-age protagonists because her growth is forced, not chosen — and therefore more honest.