Harold Crick is an IRS auditor whose mundane existence is governed by routine and numbers. He leads a life of strict order and minimal excitement, meticulously counting brush strokes as he brushes his teeth or timing his walks to the bus stop. One day, Harold begins to hear a disembodied voice narrating his life, detailing his actions and inner thoughts, as if he were a character in a book. Confused and alarmed, he tries to ignore the voice, but it persists, accurately predicting his every move and even revealing thoughts he has never uttered aloud.

As the narration continues, the voice foretells an ominous turn: Harold's imminent death. Distraught, Harold seeks help, ultimately encountering Professor Jules Hilbert, a literature expert who skeptically agrees to aid Harold in figuring out the genre of his life's story to alter the predicted outcome. In his quest for survival and understanding, Harold also begins to engage more deeply with the world around him, forming a connection with a kind-hearted baker named Ana Pascal, whom he has been auditing. This budding relationship becomes a catalyst for Harold to reassess his life, confront what has been narrated about his fate, and truly begin living instead of merely existing.