A Chicago area telemarketer named Gary Lambert thinks he sees a giant insect-like creature in the office of the vinyl siding company where he works. Skinner sends the agents to investigate after someone releases an audio tape warning of a monster hiding in the light at the company; even Mulder thinks it's a little much. After Lambert thinks he sees a co-worker get zombified, he takes the office hostage, Mulder included.
Scully arrives in Chicago after discovering a similar case in Florida in 1992. Lambert says his boss, Mark Pincus, is using turning employees into mindless drones and controlling them via telepathy, and wants to get on TV to expose him. Shortly before a SWAT team storms the building, Mulder also sees Pincus as an insect-like creature. Mulder begins to connect reports of "hiding in the light" in the X-Files, as well as the Pincus' connection with them. He wonders if Pincus is using visual hallucinations that some people can see through.
Mulder returns to Chicago, and finds that Lambert was also doing an investigation of his own; Pincus and a zombified employee shadow the agents. An autopsy of a man Lambert shot in the hostage incident appears to have been dead for longer than he actually has been. Mulder tracks Pincus to another employee's house and breaks in to try to save her, leading her to file a complaint and Mulder having a seemingly psychotic episode where he tries to save Skinner from Insect Pincus.
Mulder is secured in a hospital, and tells Scully that Pincus bites or injects his victims on the neck, and begs her to believe him. Scully looks at the body again, and finds that it has some strange marks on the neck and has been injected with some sort of toxin. At the hospital, Mulder sees Insect Pincus at the window, and a nurse is convinced to open his window. Scully arrives, sees the nurse in zombie form, and chases Insect Pincus out of the room with some gunshots. Scully reports to Skinner that Mulder is not insane, and that Pincus and several key witnesses described by Mulder as zombies have disappeared. In Missouri, another telemarketer at the company sees an insect creature at his workplace.
Cynthia Preston, who plays Nancy Aaronson, also played Faith Roscoe on General Hospital.
Episode Body Count
Gerald Resnick: a Florida church deacon who Scully says commits suicide after believing there was an evil presence among the parishioners and wounding several of them.
Mark Backus: a VinylRight employee shot by Lambert after he tries to attack him.
Gary Lambert: shot by SWAT team members when they raid VinylRight.
Cumulative Body Count (116/202 episodes, 0/2 movies)
Humans: 1,410Creatures: 88
Grand Total: 1,558