The narrator and protagonist of the novel. Fifteen-year-old Christopher is mathematically gifted struggles for social acceptance and understanding as a result of his apparent autism. He views the world largely in absolutes, dividing his life experience into a series of extreme likes and dislikes. He feels most comfortable with logic and order, making Wellington’s murder an irresistible puzzle for him to solve. He resides with his father and pet rat Toby at 36 Randolph Street.
Single father of Christopher. Father prepares meals for Christopher and sees to his daily needs. Later on, Christopher uncovers elements of his life that he has long tried to keep hidden. Father owns a heating maintenance and boiler repair business.
Christopher believes she died of a heart attack prior to the time when the novel begins. Remembered as a loving but impatient and volatile woman, she was at times overwhelmed by the difficulty of caring for her troubled son.
A neighbor of the Boones’s. Eileen Shears is the ex-wife of Roger Shears. Christopher remembers that she would often visit to cook meals and play scrabble in the wake of his mother’s death. The murder of her dog, Wellington, provides the major dramatic impetus for the novel.
Estranged husband of Eileen Shears. Roger Shears once worked at a bank in town, but moved to London rather suddenly a couple of years ago, leaving Mrs. Shears behind. His mysterious nature leads Christopher to investigate him as a possible suspect in Wellington’s murder.
Christopher’s primary teacher at school. An even-handed mentor, she works to expand Christopher’s horizons socially as well as academically. As a result, she is one of the few people whom Christopher trusts, and in the limited moments when the reader sees her, she mirrors the reader as an observer and commentator on Christopher’s life.
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An elderly resident of Randolph Street. A kind lady, Mrs. Alexander lives a quiet existence filled by caring for her garden and pet dachshund, Ivor. She exhibits grandmotherly tendencies toward Christopher, owing in part to his resemblance to her own grandson. She reveals to Christopher important information about the affairs of Christopher’s father and mother.
Mrs. Shears’s large black poodle. Largely docile until an operation left him erratic and occasionally violent, he is found dead in the opening scene of the novel with a pitchfork through his side.
Christopher’s brown and white pet rat. Christopher adores Toby and treats him as a friend and family member. He later becomes Christopher’s sole companion on his harrowing journey to London.
A middle-aged man and the psychologist at Christopher’s school.
Father’s co-worker. Rhodri is a smelly and obnoxious man who often prods Christopher with difficult math questions for his own amusement, but he also happens to be one of Father’s only social outlets.
Christopher’s first primary teacher at school.
The brother of Ed Boone. He works at a factory in Sunderland.
Mrs. Peters’s husband. A vicar, he agrees to be the invigilator (proctor) for Christopher’s A-level math exam, and so plays a key role in determining Christopher’s future.
Christopher’s school principal. Although skeptical of Christopher’s abilities, she agrees to let Christopher take his A-level math exam.
Resident of Randolph Street. Mr. Thompson is one of the many neighbors whom Christopher interviews during the course of his investigation.
A resident of Christopher’s block. Another interviewee, he lives with and cares for his disabled mother.