The unnamed Narrator is an insomniac dissatisfied with his job and lifestyle. He attends support groups for problems such as cancer. His efforts are ruined when another impostor, Marla Singer, joins the same groups. Viewing her as a mirror to his own lies, he arranges for them to attend different sessions, to which she reluctantly agrees.
On a return flight from work, the Narrator meets a soap salesman, Tyler Durden. After an explosion destroys the Narrator's apartment, he moves into Tyler's decrepit house. They become friends and start an underground fight club in a bar basement. Tyler also saves Marla from an overdose, initiating a sexual relationship between them, while the Narrator remains cold to her.
The Narrator quits his job, blackmails his boss for funds, and grows Fight Club, attracting new members, including his cancer support group friend, Bob. Tyler morphs the club into Project Mayhem, committing acts of vandalism intended to disrupt the social order. Feeling sidelined, the Narrator confronts Tyler, who admits to orchestrating the explosion in the Narrator's apartment and then goes missing. The police kill Bob during a mission. Discovering its nationwide reach and being called Tyler Durden by Marla and other people, he realizes he and Tyler are split personalities.
Learning that Project Mayhem plans to erase debt records by blowing up the headquarters of credit-card companies, the Narrator unsuccessfully warns Marla and goes to the police, some of whom are also Project Mayhem members. He attempts to disarm the explosives, but Tyler attacks him. Accepting that he is Tyler, he shoots himself in the mouth, "killing" Tyler, while the bullet non-fatally passes through the Narrator's cheek. Marla arrives, and the two hold hands as they watch the targeted buildings collapse.
