The Narrator and Tyler Durden are standing on top of the Parker-Morris building, which is rigged with explosives. Tyler is holding a gun in the Narrator’s mouth. The Narrator takes us back in time to how he ended up at this point.
The Narrator is a bored, aimless office worker whose life has become a meaningless cycle. He works as a recall campaign coordinator. He participates in the consumer-driven goals of his culture. He lives in a nice condominium apartment filled with hip, clever designer furniture. He spends his time wondering about what kind of lamps and chairs will define him as a person.
Because of the unhappiness in his life, the Narrator develops insomnia. He goes to work in a daze and after a few weeks is desperate for sleep. He goes to see a doctor. The doctor dismisses his issues and tells him that if he wanted to see real pain he should see some of the people in support groups with real problems.
The Narrator takes his advice and begins visiting support groups. He becomes addicted to them. He pretends to be afflicted with various medical issues and diseases so that he can attend meetings. Here he meets Big Bob, an ex-body builder and steroid abuser whose testicles had to be removed. During an embrace with Bob, the Narrator cries and lets go of his hope. That night, he can finally sleep. He continues to go to the groups every night so that he can cry and be comforted.
One night he notices that a woman has also been attending all the same groups. She too is obviously faking her conditions and pretending to be sick and dying. Her name is Marla Singer. With her at the groups, he can no longer cry, and so he can no longer sleep either. He fantasizes about confronting her and getting her thrown out. Instead they decide not to attend the same meetings.
The Narrator flies around the country visiting car accident sites. His company is a car manufacturer and his job is to determine if the cars they make have defects that might have contributed to an accident. His job is to assess the risk and determine if a recall is worthwhile. If out-of-court settlements cost less, no recall will be initiated.
Burned out from traveling, the Narrator takes a vacation. He visits a nude beach where he meets Tyler Durden, a charismatic man who makes soap for a living. Tyler gives him his phone number. After returning home, the Narrator finds that his condominium has blown up in a suspicious explosion. He calls Tyler, who meets him at a bar. After many drinks Tyler tells the Narrator that he can move in with him, but he has to do him a favor. Tyler asks the Narrator to hit him as hard as he can. They engage in a messy fight. This is the germination of fight club.
Tyler and the Narrator continue to fight in bars and parking lots, attracting the attention of other men. Fight club starts to grow. The Narrator begins seeing men in his day-to-day life with cuts and bruises on their faces. He begins taking less and less interest in his work, much to the chagrin of his boss. Tyler and the Narrator work a series of night jobs where they also commit acts of civil disobedience.
One night the Narrator has a dream that he is having sex with Marla Singer. The next morning Tyler tells him that he met Marla last night and the two of them had sex. The Narrator is angered. Marla was the reason he couldn’t enjoy the support groups, and she has invaded his home life with Tyler too. With Marla in the picture, he will also get less of Tyler’s attention. He comes home every day from work to hear Marla and Tyler having sex and calling each other names.
Tyler has meanwhile set up a fairly lucrative business selling soap. One night he shows the Narrator how to make soap. Using a can of lye he burns the Narrator’s hand and tells him that he has much farther to go to reach rock bottom. The Narrator, Tyler says, needs to accept that one day he will die.
Tyler and the Narrator decide that they need to blackmail their bosses for the civil disobedience they have been committing on the job. After ensuring checks will continue to be sent to them even though they won’t be working, they are able to focus all their time on fight club. The Narrator learns that Bob has also joined fight club and that there are chapters of fight club that he didn’t even know about.
Tyler decides to escalate his civil disobedience into a larger project called Project Mayhem. He recruits fight club members to join and begins amassing a large following. He hands out homework assignments for the members, including the Narrator. After a while, Tyler suddenly disappears.
The Narrator finds that everywhere he travels men seem to recognize and address him as “sir”. As he travels around the country he asks these men if they know where Tyler is. They point him toward Seattle. In Seattle, the Narrator meets a bartender in a neck brace who addresses him as Mr. Durden. The Narrator runs back to his hotel room and calls Marla to find out if the two of them have had sex. Marla is mystified by his question and upset with his behavior. He asks her what his name is. She tells him it is Tyler Durden.
Tyler “returns” and is upset with the Narrator for discussing him with Marla behind his back. Project Mayhem has begun to take on more extreme assignments and is growing in its number of members. While on an assignment, Bob is killed by a police man. His death prompts the Narrator to try to shut down fight club, but he is thrown out by its members instead.
Upon arriving at work one morning he discovers that his boss is dead. Worse yet, the Narrator knows Tyler is the one who killed him, which means that he killed him, though not wittingly. He boards a bus and tries to get away from the scene before he is spotted. The other passengers are all members of Project Mayhem. They tell him that they have orders to castrate him for trying to shut down fight club. They corner him and knock him out with ether.
The Narrator wakes up in the remains of his condominium. He has not been castrated. He decides he has to warn Marla about who Tyler really is. She may be in danger. She reluctantly meets him and tells him that he murdered someone. He says he knows about his boss but Marla tells him that he shot another man who was investigating fight club for the mayor. The Narrator has no recollection of this at the time but later begins to remember the details. Out of guilt he visits a fight club location and signs up to fight every member there. He wants to die because of the guilt he feels at the deaths of Bob, his boss, and now a third person. He passes out on the floor during a fight.
He wakes up in the house he shares with Tyler. Tyler is there. He tells the Narrator that it is time for his grand operatic death. We return to the roof of the Parker-Morris building where Tyler is holding a gun in the Narrator’s mouth. Before he can pull the trigger, Marla and the other support group members show up and tell him to stop. He warns them that the building is set to be demolished by explosives but they do not leave. Marla tells him that she likes him too. He understands that he created Tyler so that he could be with Marla. The clock ticks down to zero but there is no explosion. Despite the protests of Marla and the crowd he still fires a bullet through his cheek.
When he wakes up, the Narrator believes he is in heaven. In reality, he is in a mental institution. He sees men there with cuts and bruises who tell him that the plans are continuing and they can’t wait for him to get better and join them again.