Harold seeks help from a literary professor (Dustin Hoffman) and finally finds the author - but she doesn't believe him, and in all her books the protagonist dies in the end. Harold decides to live his life, knowing he will die soon anyway. Realising he is in a tragedy, the plot moves on when he is almost crushed by a demolition ball (the demolition experts have the wrong apartment complex), and he must move in with Dave, his only friend from work.
No longer wearing a suit, or turning up for work, he tells Maggie Gyllenhaal that he wants her - which seems to work. And when she sees him playing the guitar to "Whole Wide World" she's won over.
At the end, Harold is walking down the street when he sees that a young boy is about to be run over by a bus. He dives in the way, pushing the boy to safety but is run over.
Emma Thompson shows up to Hoffman's office to show him the revised book - and it's far from her best piece of work. But as Harold saved the boy, knowing he would die, she could not kill him off.
In hospital, we learn that he suffered a variety of broken bones - and a piece of glass from his watch was embedded into the artery in his wrist, stopping too much blood loss and saving his life.
Everyone ends up for the better - Harold pays for Dave to go to an adult Space Camp, Dustin Hoffman bombs into the swimming pool like a kid again, and Queen Latifah is off to her next assignment.