In different decades, different styles of paranoia have dominated movies and television. The '50s were famously concerned with conformity: If you weren't afraid of anthill collectivism abroad, you feared it emerging at home. The anti-authoritarian '70s took their cues from Vietnam, Watergate, and a host of ugly revelations about the FBI and CIA. In films like The Parallax View, Winter Kills, and Murder by Decree, the enemy wasn't our neighbors; it was our leaders.

And the '90s? They were the period when pop-culture paranoia went postmodern. At a time when the world's cultures and subcultures traded and blended more freely than ever before, so did its schools of fear. Militiamen, hippies, black nationalists, ufologists--the mythologies of one group flowed freely into another's, even as radically different styles of conspiracism contended. It was the perfect era for a program like The X-Files, which changed its colors from week to week: sometimes a science fiction series, sometimes a supernatural fantasy, sometimes a political thriller, sometimes a self-aware comedy. For a genre show, it had a hard time sticking to one genre.

And for a show whose lead character focused so emphatically on exposing The Truth, it found those truths in a diverse set of places. In its best years--from its debut in 1993 to around 1997--the series found conspiracies in the military, in corporate America, and, of course, in the skies. Its heroes encountered militias and vampires, hackers and disgruntled postal workers, surveillance cameras and the country's most ubiquitous species of shadow government: a neighborhood association and its Covenants, Conditions, and Restrictions. If a popular anxiety was afoot--justified or unjustified, conspiracist or more broadly paranoid--it turned up in The X Files. (Sometimes the franchise managed to catch a fear before it entered the larger culture. The debut episode of a short-lived spinoff, The Lone Gunmen, featured a plot to crash a jet into the World Trade Center.)

The '90s were also a time of ironic paranoia, of a surrealist subculture less interested in exposing secret plots than in using conspiracy theories as a joke or a metaphor. This, too, turned up on the show. Several witty episodes, most of them scripted by Darin Morgan, cast doubt on the very notion of a single Truth--or, at least, of a Truth that can be captured in one master narrative.

At the same time, the series attempted to build such a narrative. This proved the show's undoing. The grand conspiracy that once stayed in the background--more an enticing set of hints than anything else--began to intrude more and more, and good storytelling gradually gave way to a plot that seemed less interesting with each new revelation. The first half of Sunday night's final episode was set in a courtroom (a secret military tribunal, of course), where a trial allowed the chief characters to summarize the vast conspiracy they'd uncovered. After this had gone on for a while, the judge asked angrily, "Is this leading anywhere?" What longtime X-Files viewer has never exclaimed the same thing?

The X-Files was not the best TV series of the '90s. Nor was it the most popular. It wasn't even the most paranoid. (That honor properly belongs to Seinfeld.) But it reflected the Zeitgeist--many Zeitgeists--for several years, before it dribbled away at the end. Those who missed the final episode, allegedly dedicated to summing up and clarifying the conspiracy, will not be surprised to learn that it opened new plot holes and left yet more questions unanswered. It was a sad spectacle, but a perversely satisfying one: At least the beast was put out of its misery. Paranoia is a powerful muse; surely it will find a new outlet.