Atrapado en una espiral obsesiva con el Número 23, Walter Sparrow convierte su vida que alguna vez fue idílica en un auténtico infierno de tortura psicológica que podría conducirlo a su propia muerte, e incluso provocar la de sus seres queridos. Estimulado por una misteriosa novela, Número 23, a la que no se atreve a dejar de leer, Walter se ve obligado a descifrar los secretos de su pasado antes de poder proseguir su futuro con su esposa, Agatha y su hijo adolescente, Robin.

On his birthday, Walter Sparrow, an amiable dog-catcher, takes a call that leaves him dog bit and late to pick up his wife. She's browsed in a bookstore, finding a blood-red-covered novel, a murder mystery with numerology that loops constantly around the number 23. The story captivates Walter: he dreams it, he notices aspects of his life that can be rendered by "23," he searches for the author, he stays in the hotel (in room 23) where events in the novel took place, and he begins to believe it was no novel. His wife and son try to help him, sometimes in sympathy, sometimes to protect him. Slowly, with danger to himself and to his family, he closes in on the truth.