Tom, a writer and loner going into his senior year in high school, is without friends; and to make it worse, he discovers he has cancer. That all soon changes. In a series of letters to his former friend Caleb, he discusses his coming-of-age experiences of falling in love, gaining friends, and becoming close to eleven-year-old Noah who also suffers from cancer. Tom slowly learns the meanings of life, his purpose, and what it means to be happy and make an impact.