Platt is the eldest of the Barbour children. When he is a teenager he is a “champion lacrosse player and a bit of a psychopath,” who torments Andy mercilessly. Later, Platt explains that he was sent to boarding school at a very young age in order to hide the truth of Mr. Barbour’s bipolar condition from him. As an adult, Platt gets a job at an academic publishing house. He is deeply changed by the deaths of his father and brother, and develops a drinking problem. However, despite his troubles, he is deep down a kind person who regrets his cruel treatment of Andy and treasures his friendship with Theo.