Christopher, a fifteen-year-old boy from Swindon, lives with his father. He has Asperger's syndrome, a form of autism. Christopher is passionate about math, science, and Sherlock Holmes, but struggles to understand others. When he discovers a dead dog on his neighbor's lawn, he decides to solve the case and write a detective story about it. Like all good detective novels, the more he uncovers, the more complex the mystery becomes—both for Christopher and his family.