A few TV shows of recent times can be said to have had a profound effect on the medium and the broader culture, something more significant than mere ratings and popularity: Twin Peaks, The Simpsons, ER. But has any programme ever had such an overwhelming influence as The X-Files?

First broadcast in September 1993, this downbeat, macabre drama followed the adventures of FBI Special Agents Dana Scully (the sceptic) and Fox Mulder (the believer). Originally shot in Vancouver before transferring production to Los Angeles, it used murky lighting, enigmatic dialogue and a memorably spooky theme tune to build up an unsettling atmosphere where nothing was as it seemed and reality -- or, at least, our perception of it -- was a malleable thing, routinely manipulated by shadowy forces. As the show's tagline exhorted, "Trust no-one".

The X-Files soon achieved a rare hat-trick: huge ratings, critical acclaim and a devoted, almost fanatical, cult following (the internet, for example, hosts hundreds of dedicated fan sites for so-called 'X-philes'). The show's two main stars, David Duchovny and Gillian Anderson, were nominated for Emmy awards (Anderson won in 1997) and both carved out respectable film careers on the back of their small- screen success.

It inspired a spin-off series (The Lone Gunmen), a smash-hit movie and then another which hits our screens next Friday (The X-Files: I Want to Believe). By its final episode, it was the longest- running sci-fi show in the history of American television. It was declared the second greatest cult show of all time (after Star Trek) by the influential TV Guide magazine, while Entertainment Weekly named it the fourth best show of the last quarter-century.

popular

Science fiction has always been popular among a certain demographic, but The X-Files managed to both broaden the genre's borders and reach a far wider audience than could be expected.

It tapped into communal paranoia, the burgeoning phenomenon of the conspiracy theory and end-of-the-millennium hysteria, with its bizarre tales of alien abduction, scientific anomalies and shadowy government cover-ups. People want to believe in weird things, in the power of the paranormal and massive invisible conspiracies which are controlling our lives, and The X-Files gave them plenty to go on.

For maybe the first time, someone seemed to be taking the 'weirdos' seriously. It was absolutely perfect television for our panicky, suspicious, volatile times.

A flood of strange, off-kilter programmes -- many of them concerned with the supernatural -- such as American Gothic, Carnivale, Dark Skies, The 4400, Dark Angel and Millennium followed, and it's hard to see them having being made without the influence and popularity of their forebear. Similarly, the programme's use of a lengthy, over-arching narrative or "mythology", which formed a macro-foundation for the weekly stories, was copied by many successful shows such as Lost, Heroes, 24 and Alias. Even something as seemingly different as Buffy the Vampire Slayer owes a debt: its creator, Joss Whedon, has described his show as a cross between The X-Files and My So-Called Life.

revelation

Of course, it didn't last. After nine series The X-Files had probably run out of steam, and was euthanised at the right time. One particular problem was the "tease" factor: the way the audience was constantly promised the definitive, amazing revelation which would explain everything and tie up all the loose ends, but which never materialised. We were offered tantalising glimpses of "the truth" but never the whole thing, leading sceptical viewers to conclude that the writers probably didn't know it themselves.

Still, it ended on a decently dramatic note, with the right touch of open-endedness. And multi-channel reruns, the big-screen revival and countless online devotees will keep the cult alive into perpetuity. The X-Files may be closed, but the truth, we believe, is still out there.

- Darragh McManus