The agents cross paths with a pair of doppelgangers whose close proximity leaves a trail of destruction.
In Kansas City, two missionaries visit two women at two different homes in the same neighborhood that look exactly alike. The second woman yells at them to go away and the two men, inexplicably, get into a fight in the woman's front yard. Two agents that look similar to Mulder and Scully (and sound exactly like them) visit the first woman, Betty Templeton, whom claims to have never seen the other woman before. That woman then passes her by in a car and the two agents begin fighting each other. They then crash into a tree, putting both agents in critical condition. Both agents said that they were possessed and worked together for seven years. The other woman, Lulu Pfeiffer, applied for a job at Koko's Copies, but did not get the job because she had 17 jobs in 17 states in three years and moves a lot. She becomes aggravated and everyone's copies become black, resulting in the manager hiring her anyway, presumably to help out in the ensuing chaos of angry customers. The other woman goes to another job with the same name and same resume.
Mulder and Scully visits Bert Zupanic to ask him about the disappearance of Templeton, but he claims he never saw her. Later, in a bar, Zupanic comes across Templeton. Moments later, Lulu walks into the bar and an earthquake occurs that breaks all the glass in the bar. Lulu then runs out. Mulder finds out through Argyle Saperstein that Zupanic and one of the women are in a relationship and that Zupanic is a professional wrestler. Scully finds that for the past 12 years the women have followed each other across 17 states and left mayhem in their wake. Saperstein calls Zupanic and it is revealed that Zupanic owes Saperstein money and that Betty and Bert are having a relationship and he has been having an affair with Betty. After Lulu leaves, gunshots ring out in the floor about Zupanic. Zupanic and Saperstein meet at a bar to exchange money and an earthquake occurs in the bar before Lulu walks in. Betty comes out of the bathroom and another earthquake occurs. Lulu and Betty see each other in the bar and the glass in the bar begins breaking again before both women leave. Zupanic is knocked unconscious and Saperstein takes the money and leaves.Betty tells Mulder that Lulu is causing all of the problems and forcing her to leave. Lulu told Scully the same thing. The women pass each other and a sewer grate blows, sucking Mulder into the storm drain, and then closing the grate, sealing him in for the day. Scully finds that the girls share the same father who's in prison. The man, Bob Damphouse, is insane. Zupanic thinks he lost the money and Betty uses the copy machines at work to counterfeit money. Meanwhile, Mulder finds his way out of the storm drain he was sucked into earlier. At the prison, Scully meets a man that looks exactly like Bert Zupanic, while Betty brings the money to Zupanic's fight. Lulu and Betty meet at the fight and everyone in the audience breaks into a fight. The other Bert Zupanic shows up and everyone stops fighting. The two Zupanic's see each other and a fight breaks out again. Mulder and Scully are shown bruised and beaten later.
- Steve Kiziak (First Agent) previously played Steve in The X-Files episode "Hungry" and David Duchovny in "Hollywood A.D.".
- The episode title, and possibly its plot, is a reference to the 1999 film, Fight Club.
- Randall "Tex" Cobb as Bert Zupanic
- Art Evans as Argyle Saperstein
- Jack McGee as Bob Danfous
- Rob Van Dam as Opponent
- Gene LeBell as Freddie
- Kathy Griffin as Betty Templeton/LuLu Pfeiffer
- Brian Chenoweth as Tom
- Jim Hanna as Tim
- Nicole Bush as First Customer
- Paul Hansen Kim as Second Customer
- John Mack as Third Customer
- Arlene Pileggi as Second Agent
- Steve Kiziak as First Agent
- Cory Blevins as First Missionary
- John O'Brien as Second Missionary
- Christopher Michael as Trusty