Christopher’s book begins as a mystery novel about the murder of his neighbor’s dog, but as Christopher’s investigation progresses, it comes to represent Christopher’s search for the truth about his mother and father. As Christopher searches for clues about Wellington’s murder, he finds evidence revealing that his father has been lying to him about his mother’s death. Investigating Wellington’s murder becomes an excuse for Christopher to uncover the secrets that Father has kept from him, and Father’s deception acts as a crime in itself. Ultimately, we learn that Wellington’s murder and Father’s deception constitute separate parts of the same investigation. Father lied to Christopher in large part because of the feelings of loss and anger he felt when Christopher’s mother left him. When Mrs. Shears broke off her affair with Father, those same lingering feelings of loss and anger caused him to lose control and kill Wellington. Christopher’s search for the truth about Wellington essentially leads him to the truth about his mother and father.
Logic puzzles, math problems, and maps symbolize to Christopher the part of the world that is ordered and logical. Accordingly, Christopher uses these items as tools to organize his thinking, like when he uses the so-called Monty Hall problem to explain why his intuition regarding Mr. Shears has been wrong, and they serve as Christopher’s primary means of achieving a sense of security. These items recur continually throughout The Curious Incident of the Dog in the Night-time, but they appear most often when Christopher encounters new information that he has not fully processed, or when he experiences a particularly confusing or disturbing event. When his thoughts become jumbled in the train station in Swindon, for instance, Christopher thinks of the visual riddle called Conway’s Soldiers to pass the time. He also regularly uses maps to navigate and achieve his goals. He uses a map when he searches the neighborhood for Wellington’s murderer, again when he attempts to find the train station in Swindon, and yet again in his effort to find Mother’s apartment when he arrives in London. In essence, these different items provide Christopher with a strategy to follow when a problem involves too many variables for him to reach a clear solution.
For Christopher, the A-level math test represents a way for him to validate and feel proud of himself. Because of his condition, Christopher is socially inept and attends a school for children with disabilities. But Christopher does not feel that the other children in the school are really his peers. His condition, while a handicap, doesn’t limit him to the extent that the other children’s disabilities limit them. Christopher recognizes this fact and also knows that he is exceptionally gifted in math and science, causing him to feel generally superior to his classmates. Christopher, however, seeks to prove this superiority, and the A-level math test gives him the opportunity. His preoccupation with the test in the later sections of the novel shows how much he wants the opportunity to prove his ability.