The protagonist goes through remarkable growth and maturation over the course of the story. At the beginning of the novel, he is self-absorbed and miserable in his new surroundings and speaks of his intellectual disabled sister, Natalie, in not-so polite terms. His main focus is on the injustice of his situation. However, it is clear from the start that he is a responsible kid who follows the rules, and that he deeply loves his sister.

Because of his family’s financial circumstances, Moose must care for his sister. By including her in their daily activities, Moose makes Natalie a part of his friend group and all of this extra time with her allows him to see things from her point of view. He becomes more concerned for her wellbeing, even speaking out to his mom and breaking the rules of no contact with prisoners by writing Al Capone a letter to try and help Natalie. His special relationship with his sister proves that he can empathize with others and he becomes less self-centered as the novel goes on.