The story is set in Swindon, a small town in southwest England. One day a few minutes after midnight, the narrator, a fifteen-year-old autistic boy named Christopher Boone sees a dead dog on the lawn in front of the house of Mrs. Shears, a neighbor. The poodle has a garden fork sticking out of it, and Christopher assumes the dog, whose name was Wellington was killed by the fork. He wonders who killed the dog, and why.
Christopher introduces himself and explains how his teacher Siobhan, when she first met him eight years ago, showed him lots of emoticons, but he had difficulty in understanding the feelings each emoticon was conveying.
Christopher touches the dog and strokes it. He removes the fork from it and hugs it. Mrs. Shears emerges from the house screaming and asks him what has he done to her dog. Christopher lets the dog go and steps back.
Analysis, chapters 2–5
The chapters of the book are numbered in an unusual way, using only prime numbers. A prime number is a number that can be divided evenly only by 1 or itself. (Christopher will explain his numbering system later.)
The opening sections set the scene for the murder mystery that will follow. Unusually, the victim is a dog rather than a human, but this interests Christopher because he likes dogs and has a harder time relating to humans.
These sections also reveal something about Christopher, the teller of the tale. He is brilliant at mathematics and knows every prime number up to 7,057. He also has the ability to retain a huge amount of factual information; he knows the names of all the countries in the world and their capital cities. But he has difficulty in reading other people’s emotions and relating to them in a normal way. He does not know how to react when something unexpected happens and tends to try to close it off. For example, when Mrs. Shears screams, he puts his hands over his ears, closes his eyes, and doubles over and presses his forehead in the grass. In situations like this, he just has to shut down, as much as he is able to.