Christopher, 15 years old, narrates the tale. He has high-functioning Autism, thinks in very orderly patterns, likes routines, possesses a keen interest in mathematics and science, and is highly observant. He takes it upon himself to solve the murder of the dog Wellington; in the process, he embarks on an adventure filled with wonder and terror—a journey that tests his ability to cope with a frightening world. To Christopher, other people are largely a mystery: He can’t decipher their facial expressions, and he finds confusing their informal, inaccurate ways of speech. Trying to figure them out is impossible in a crowd, where he feels overwhelmed and terrified.

Christopher prefers things to be orderly; he relishes truth and hates lies, and math and science are a haven from the chaos of human interactions. He is extremely intelligent, precisely logical, and possesses tremendous determination when he resolves to achieve something. He must overcome serious emotional obstacles to solve the mystery of the dog’s death, reunite with his mother, and reconcile with his father. 

Christopher’s father, Ed Boone, owns a small business doing heating repair and maintenance. He tends to eat too much and drink a lot of whisky. For a time, after his wife leaves him for neighbor Roger Shears, he has an affair with Roger’s ex-wife, Eileen.