The Story. Christopher finds a neighbor's dog, named Wellington, murdered. With the help of his teacher, Siobhan, he decides to write a book about his attempt to solve this mystery. During his investigation, Christopher meets people living on the same street but whom he has never met before. He eventually discovers that Mr. Shears, a neighbor, had an affair with his mother, Judy. Christopher records this as well as other discoveries.
His father, Ed, discovers his writings and confiscates them but the son tries to find them back. In his search, Christopher finds letters from his mother which his father had hidden. Supposedly, Judy had died of a heart attack as told by Ed, and now Christopher comes to know that she is still alive. He is quite shocked that his father would lie to him about this. On the bed, he vomits and groans until his father comes back.
Realizing that Christopher had read the letters, Ed cleans up Christopher and then tells him the truth about Judy and confesses to killing Wellington in his anger to Mrs. Shears. Christopher, however, feared that his father may also kill him, and so decides to get away and look for his mother. He embarks finally on an adventurous trip to London, guided by his mother's address from her letters. With Christopher with her, Judy eventually leaves Mr.