Mattie Burns can't keep up with her life. Her parents are too controlling, her best friend continually drags her everywhere, and her ex-best-friend insults her every time they meet. When her school starts the Penpal Project, Mattie diligently writes to her penpal. Through a span of days, she opens up to her penpal, who offers her genuine advice and seems to know exactly what to say. They advise her on bullies and crushes, on her controlling parents and making her own decisions. Then, Leroy Brooks starts appearing in her life—stopping her in the hallway to say hi or offering her his sweatshirt—and seems to know things only Mattie's penpal would know, which leads Mattie to wonder: Is Leroy her penpal?