It was written by Howard Gordon, directed by David Nutter, and featured guest appearances by Bradley Whitford, Leland Orser and Shawnee Smith.

The show centers on FBI special agents Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) who work on cases linked to the paranormal, called X-Files.

Dr. Adam Pierce, a scientist at the California Institute of Technology in Pasadena, intercepts a visual transmission from Firewalker, a mobile robot sent by a volcanic research project on Mount Avalon near Bend, Oregon.

They discover the seemingly traumatized team: robotics engineer Jason Ludwig (Leland Orser), systems analyst Peter Tanaka (Hiro Kanagawa), and graduate student Jessie O'Neil (Shawnee Smith).

An autopsy by Scully finds sand (silicon dioxide) in his lungs, indicating the existence of a silicon-based lifeform; she theorizes that the organism infects the nearest hosts or otherwise dies.

Trepkos tells Mulder that after Firewalker returned from its first descent, Erickson pulverized a rock in one of its samples, resulting in his death and the infection of all the scientists immediately surrounding him.

[1][2] Howard Gordon was inspired to write the episode after seeing two news reports about Project Dante, a robotic explorer created by NASA that had been sent into a volcano.

[4] However, Gordon felt that the episode allowed him to explore the possible results of Mulder's search for the truth, echoing this in the mindset of Daniel Trepkos and the interactions between the two characters.

Gordon noted that "the natural endpoint of this quest for the truth is madness", comparing Mulder's treatment of Trepkos with the events of the novel Heart of Darkness.

The set used for the exterior of the field base camp was later sold to the production company responsible for the TV series The Sentinel, while the interior was shot inside a British Columbia hydro sub station.

Club, Zack Handlen felt that "Firewalker" represented a "back to basics" approach to the series, following from the previous story arc relating to Scully's abduction.

Handlen noted that the episode would have been "a total waste of time" elsewhere in the season's schedule, but served as a "competent enough" means of reuniting the main characters.