In the novel The Curious Incident of the Dog in the Night-Time, Christopher Boone, a brilliant teenage boy with Autism, sets out to solve the murder of his neighbor’s dog. Written by Mark Haddon and published in 2003, the book has become a prize-winning bestseller translated into three-dozen languages. Already considered a classic, the work has been adapted as a stage play and is performed internationally. The e-book edition is the basis for this study guide.

Plot Summary

Fifteen-year-old Christopher Boone, out walking in his Swindon, England neighborhood late one night, discovers a poodle dead on its front lawn, impaled on a garden fork. The dog’s owner, Mrs. Shears, calls the police, who arrive and question Christopher, who curls into a ball on the lawn; when one of them tries to lift him, Christopher strikes the officer. The officers arrest him and take him to a police station holding cell. Christopher’s father bails him out and brings him home. Christopher decides to solve the mystery of the dog’s murder. In the ensuing days, he visits the neighbors, asking if anyone knows anything about the killing. His father makes Christopher promise to stop investigating.

Christopher is determined to take the A-level math exams, which will help him get into college, and his father arranges it. One of Christopher’s teachers, Siobhan, suggests he write about his experiences, and he begins keeping a journal, which becomes the novel. It includes an account of his investigation, his experiences at school and home, and random thoughts about math, science, Sherlock Holmes, and the strangeness of people. Christopher describes his techniques for getting along with others despite his inability to read faces or understand the highly metaphorical language that most people use. Christopher also writes that, two years earlier, his mother disappeared. His father explained at the time that she died from a heart attack in the hospital.

Christopher reasons that his promise not to investigate contains loopholes; quietly he continues his detecting. He learns from a neighbor, the elderly Mrs. Alexander, that Mr. Shears had an affair with Christopher’s mother.

His father finds and reads Christopher’s journal and becomes angry that Christopher has broken his promise. He grabs Christopher, who hates being held, and a fistfight erupts; Christopher gets knocked out. Regaining consciousness, he sees his father removing the journal.

Remorseful, his father apologizes to Christopher and treats him to a weekend trip to the zoo. On Monday at school, Siobhan sees the bruise on Christopher’s face and asks if he’s afraid of his father, but he says no. Back at home, Christopher searches the house for his book and finds it hidden in his father’s bedroom. Beneath the book are a series of letters addressed to Christopher from his mother. He reads them and realizes she didn’t die but moved away with Mr. Shears. Shocked by his parents’ betrayals, Christopher throws up and falls asleep. His father finds Christopher and helps him clean up. His father then confesses that, after Christopher’s mother left, he had an affair with Mrs. Shears, but they argued, she kicked him out, and her eccentric dog had attacked him; enraged, he killed the dog. On learning this, Christopher screams, and his father retreats.

Christopher fears his father might kill him, too, so he hides overnight in the backyard, then steals his father’s bank card and heads for London. He has memorized his mother’s address and intends to live with her. His first solo trip from his neighborhood is terrifying for him, but he finally makes it to his mother’s flat. She and her boyfriend, Mr. Shears, find Christopher waiting for them in the rain. His mother is overjoyed; they bring him inside and shelter him for the night, but his father and the police try to retrieve him, and Mr. Shears doesn’t want Christopher to live there. Christopher’s mother, determined to stick with her son, moves with him back to Swindon in a cheap rental apartment.

Despite the chaos, Christopher manages to take the A-level math exams and earn an A grade. His mother finds a new job, and they go for visits to his father’s house. His father gives him a puppy, and, over several weeks, father and son repair their rift. Christopher notes happily that he has solved the dog’s mystery, found his mother, passed the pre-college exam, and written a book. He knows now that he can achieve anything.

The book is divided into 51 chapters, each named for a prime number. Thus, the first chapter is “2,” the second chapter is “3,” the third chapter is “5,” etc.; the final chapter is “233.” This guide lists the chapters using the author’s numbering system.