Peak is the novel’s protagonist and its point-of-view character. The narrative is structured as entries in his journal for an English assignment. Peak is 14 when the novel begins. He has been raised in both Wyoming and Manhattan by his mother, Teri, and his stepfather, Rolf. His parents taught him to climb. Once he moves to Manhattan, however, he resorts to illegally climbing skyscrapers in the absence of mountains. Peak is skilled but impulsive, willing to take risks in order to feel the thrill that only climbing provides. He is a good person and a loving brother and son. Other than climbing, he wants nothing more than to have a stable home life. He craves adventure, but he is also still a teen and wants the emotional security of having parents he knows will be there for him.

He is initially disillusioned when he realizes that his biological father has ulterior motives for helping him, but the pain is lessened when he is able to stop viewing Josh as a father figure. Peak knows that he does not want to be as selfish as Josh is, and he demonstrates this through his sacrifice for Sun-jo.