In the film: the Narrator discovers that he and Tyler are one and the same, so he shoots himself in the head, and he and Marla watch everyone get a clean financial slate as buildings explode around them.

In the book: The Narrator still shoots himself in the head to stop Project Mayhem, the epilogue says that he thinks he’s died and gone to heaven. In reality, he’s in a mental hospital, with Project Mayhem members as his orderlies, who all hope that Tyler will return.