ill Ferrell shifts from his usual antics to play sweater-and-slacks-clad Internal Revenue agent, Harold Crick. He's alone. He's unloved. He is, after all, the tax man. His favourite word is "integer." His teeth get precisely 78 brush-strokes each morning. His apartment is as plain as a motel room. His life is pure sameness. But one day, out of the blue, he hears a woman’s voice narrating his life, but “accurately” with “better vocabulary” than he possesses - and with a British accent.

If this isn’t enough, the invading voice – which at first he thinks is coming from his toothbrush - announces that he’s about to die. And since the voice has been precise thus far, the news cranks his anxiety up to the point where he is compelled to track down the writer and persuade her from writing his ugly demise.

After screaming "Shut up!" into the sky a few times, he sets out to find help. It hasn't occurred to dull-as-dishwater Harold that he just might be going crazy, though a psychiatrist (Linda Hunt) diagnoses him as schizophrenic. He employs Professor Jules Hilbert (Dustin Hoffman) to help track down the mysterious voice.

As it turns out, Karen Eiffel, a talented but depressed novelist who’s famous for killing her protagonists, is Harold's author. In fact, the story suggests that the reason Harold's life has been so monotonous lately is that Karen has a deadly case of writer's block and can't figure out a way to kill her novel's Harold.