Walter Sparrow is an animal control officer married to Agatha, with their son, Robin. Walter fails to catch stray dog 'Ned' and is late to meet Agatha. Agatha ends up browsing a bookstore and begins reading a book titled "The Number 23" written by Topsy Kretts. She later gives Walter the book as a birthday present. Walter starts reading the book and notices similarities between himself and the main character, a detective who refers to himself as "Fingerling." As Walter continues reading, he envisions himself and those closest to him as the book's characters, himself as Fingerling and Agatha as Fabrizia, Fingerling's new girlfriend etc.