Walter Sparrow (Jim Carrey), an animal control officer, is introduced by his wife Agatha (Virginia Madsen) to a mysterious book: The Number 23. As Walter continues to read it, he notices startling similarities between the plot of the book and the events in his own life. The book's main character, a detective called The Fingerling, explains that his name came from a children's book he once read; Walter shortly thereafter finds this same book. The book continues to chronicle the life of a character called "The Suicide Blonde", a woman who is driven to insanity by the presence of the number 23 in all aspects of her life. Agatha and her son Robin (Logan Lerman) discover that by reading the 23rd word of every 23rd page, secret messages are spelled out. These messages lead Walter into a chaotic chain of events that furthers his paranoia, eventually leading him to the realization that he himself was the author of The Number 23 during his stay in a mental institution after his father's death, whose suicide note was comprised entirely of numbers adding up to 23.