The main character in Mark Haddon’s The Curious Incident of the Dog in the Night-Time is Christopher Boone, who is also the narrator. Christopher is a 15-year-old boy who is highly intelligent but has behavioral problems. The narrative suggests that he is neurodivergent; the book does not specify a particular condition or syndrome, but it is likely that Christopher has a condition such as Asperger’s or autism. Christopher frequently struggles to understand other people and relies heavily on math and reasoning to put the world around him into an order he can understand. 

The most important secondary characters in the novel are Christopher’s parents, Ed and Judy, who each deal with Christopher’s behavioral problems in different ways. For the first half of the novel, Judy only appears in flashbacks because Ed has told Christopher that Judy is dead.