It was directed by Rob Bowman, written by Carter and Frank Spotnitz and featured five main characters from the television series: David Duchovny, Gillian Anderson, Mitch Pileggi, John Neville, and William B. Davis reprise their respective roles as FBI agents Fox Mulder and Dana Scully, FBI Assistant Director Walter Skinner, Well-Manicured Man, and the Cigarette-Smoking Man.

The story follows agents Mulder and Scully, removed from their usual jobs on the X-Files, and investigating the bombing of a building and the destruction of criminal evidence.

Carter decided to make a feature film to explore the show's mythology on a wider scale and appeal to non-fans.

Carter assembled cast and crew from the show, as well as some other, well-known actors such as Blythe Danner and Martin Landau, to begin production on what they termed "Project Blackwood".

during the Ice Age, in what will become North Texas, two cavemen hunters encounter an extraterrestrial life form in a cave, which kills one and infects the other with a black oil-like substance.

That evening, Mulder is accosted by paranoid doctor Alvin Kurtzweil, who explains that the "victims" were already dead and that the bombing was staged to cover up how they died.

Meanwhile, The Smoking Man goes to Texas, where Dr. Ben Bronschweig shows him one of the lost firefighters, who now has an alien organism residing inside his body.

Mulder and Scully travel to the site of the hole in Texas, finding it has been hastily turned into a new playground, and encountering the boys whose friend fell inside.

Driving in the direction indicated by the boys, the pair encounters a train with white gasoline tankers and follow it to a cornfield surrounding two glowing domes.

As Mulder leaves, the Well-Manicured Man shoots his driver and then kills himself in a car bomb before his betrayal of The Syndicate is discovered.

Forty-eight hours later, Mulder finds Scully in an underground facility in Antarctica which also contains many humans suspended in ice-like enclosures.

After five successful seasons, Chris Carter wanted to tell the story of the series on a wider scale, which ultimately meant creating a feature film.

[6] During production, the filmmakers went to great lengths to preserve secrecy, including printing the script on red paper to prevent photocopying,[4] and leaking disinformation to the media and giving the film the codename "Project Blackwood".

Sackheim hired executive producer Lata Ryan, who had previously collaborated with Steven Spielberg for his 1993 film, Jurassic Park.

Once hired, Ryan was allowed to read the script in front of the Ten Thirteen Productions staff members—but not to take it away.

After Ryan accepted the offer of becoming executive producer, Chris Nowak was hired as production designer, Ward Russell as director of photography and Bill Liams as construction coordinator.

While gathering research materials, they learned that the Earth was once covered with ice and decided to open the film in Texas in 35,000 BC with human "Primitives" as the first characters to appear.

Nowak was a former architect who had worked as a professional theater set designer for eight years, before moving towards the film business as an art director.

Nowak started by creating artwork for all the major sets and locations, working with the two concept artists Tim Flattery and Jim Martin.

[4][9] The tighter schedule, with only eight weeks of pre-production and 45 days of principal photography, still caused the production to have less location shooting than planned.

Due to the demands of the film shoot on the actors' schedules, some episodes of the fifth season did not revolve around both Mulder and Scully but just one of the two lead stars.

The most substantial difference was that Snow used MIDI files to save his musical scores and pieces, which would afterward be sent to a copyist who would take it through one of their programs and eventually give it to the orchestrators.

[17] The film was distributed by 20th Century Fox and premiered theatrically in the United States (as well as Canada) on June 19, 1998, along with Disney's Mulan.

"We are working on packing the [re-issued] DVD and Blu-ray releases with as many extras as they will fit, including video and audio commentaries, behind-the-scenes footage, bloopers, trailers, a new documentary, and several other cool surprises.

[30] Audiences surveyed by CinemaScore gave the film a grade A− on scale of A to F.[31] "The X-Files" movie does answer one question raised in the show for an hour a week, five years running: Is the government conspiring to keep the truth about extraterrestrials from the public?

[35] San Francisco Chronicle reviewer Bob Graham was positive towards the film, calling "David Duchovny and Gillian Anderson [...] enormously sympathetic heroes.

"[21] Michael O'Sullivan, a reviewer from The Washington Post called the film, "stylish, scary, sardonically funny and at times just plain gross.

"[36] Los Angeles Times reviewer Kenneth Turan felt that it was difficult to make sense of the film, saying that it relied too heavily on the series' mythology.

"[38] Variety reviewer Todd McCarthy remarked, "As it is, the pic serves up set-pieces and a measure of scope that are beyond TV size but remain rather underwhelming by feature standards.

"[39] Janet Maslin of The New York Times responded negatively towards the film, opining that it was uneventful and scorning the "hush-hush atmosphere" surrounding the production.