Walter Sparrow is a family-man married with Agatha Sparrow, and works catching dogs in the Department of Animal Control and has a teenager son very close to his wife and him. On the day of his birthday, he is bitten by a dog and comes late to meet Agatha. While waiting for him, Agatha buys a detective book with a novel about the mystery around the number 23 in a bookstore as a gift to Walther. He becomes captivated with the story and obsessed with the number 23, finding many coincidences with his own life, and he decides to find the author, believing the story is about him. His further investigation discloses a mysterious situation that makes Walther paranoid.