One of Scully's friends from the FBI academy, now working in the Violent Crimes Unit, asks her to assist him on a homicide investigation involving no clear point of entry. Mulder realizes that this is similar to a series of X-Files case that have occurred every thirty years, and joins in the investigation to stop the latest cycle.
Writer Glen Morgan once read an article about Richard Ramirez, a convicted serial killer who terrorized California in the first half of the 80's. Before his capture it was rumored that he entered the homes of his victims by the small window in the bathroom. This rumor would later be debunked after his arrest, but the story intrigued Morgan so much that it was the basis for the creation of the character Eugene Victor Tooms. To flesh out the story, the writers drew their inspiration from Jack the Ripper and a large ventilation shaft outside their office.
Eugene Victor Tooms returns later in Season 1, in the episode entitled "Tooms".
Mulder: This is a nest. Look, its made out of rags and newspapers.
Scully: This looks like the opening. Think there's anything inside? Oh my God, Mulder... it smells like.... I think its bile.
Mulder: Is there anyway I can get it off my fingers quickly without betraying my cool exterior?
Episode Number: 3
Season Number: 1
First Aired: Friday September 24, 1993
Production Code: 1X02