The series centers on FBI special agents Dana Scully (Gillian Anderson) and her new partner John Doggett (Robert Patrick)—following the alien abduction of her former partner, Fox Mulder (David Duchovny)—who work on cases linked to the paranormal, called X-Files.

In this episode, Scully, working alone, pursues a cult that worships a slug-like organism that it believes it to be the Second Coming of Jesus Christ.

Several of the scenes were so gruesome that producer Paul Rabwin later noted that some of the cameramen "start[ed] to lose it" during filming.

Later, at a pay phone, she asks her partner, John Doggett (Robert Patrick), to check the X-Files for cases mentioning glycoproteins.

A man with an injured hand learns that she is a medical doctor and fills her car with gasoline laced with water.

Scully goes to find a car but, moments after leaving, Hank immediately tells the townspeople what she is up to and that "another swap" is needed.

Concurrently, Doggett arrives in Utah and informs the Sheriff about a series of X-Files involving similar back wounds and death by stoning.

Later, Scully is packing her things in the hospital when Doggett comes in to inform her about the trial of the cult members; they are offering little defense except that they claim that they are being persecuted for their religious beliefs.

[2] "Roadrunners" was written by Vince Gilligan and was inspired by the thriller film Bad Day at Black Rock (1955).

[3] The script, called "uncharacteristically brutal" for Gilligan—who had been noted for his comedic episodes like season five's "Bad Blood"[4] and "X-Cops"[5]—was written with the expressed intent to make, according to Gilligan, "a really all-out scary, creepy, get under-your-skin—literally and figuratively—X-File.

[9][10] Hardy was offered the role after an unknown individual working at The X-Files saw his TBS remake of the film High Noon.

To create the illusion that the creature was crawling up the body, the fiberglass was placed on top of Anderson, and then the animatronic slug was pressed against the fake back.

[6] Anderson later described the scene as "fun to shoot", although she also called it "exhausting" because she had to struggle on the bed, all the while tied down, with her arms being attached to the headboard and her legs to the footboard.

[17] Harrisson praised the character development in "Roadrunners" and noted that the episode "effectively brings [Scully and Doggett] together as partners.

"[17] Robert Shearman and Lars Pearson, in their book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated the episode four stars out of five.

It's the transition of Gillian Anderson's performance from wry exasperation to outright paranoia ... which makes this so effective.

[19] Paul Spragg of Xposé wrote positively of the episode, saying it features a "return to the body horror stories that had worked so well in the early seasons".

George Avalos and Michael Liedtke of the Knight Ridder Tribune wrote that the episode's slug "continued the series' fine tradition of monsters that made us queasy as we squirmed in our seats".

"[21] Sarah Stegall highly criticized the episode, calling it "a bad mix of The Fly and The Kindred, with plenty of X-Files classic paranoia but none of the finesse we've seen before.