NORTH VANCOUVER, British Columbia — There they were in the midst of what looked like a spooky old-growth forest (Princess Park, actually, mere blocks from upscale suburban homes here), surrounded by clumps of moss, overgrown ferns and gigantic Douglas firs, looking for clues of yet another allegedly paranormal crime, the kind they used to solve almost every week. They addressed each other, as they always had, by only their last names.

“Mulder,” said Gillian Anderson, reprising her role as the F.B.I. agent Dana Scully, the look on her face instantly recognizable; part reprimand, part in-spite-of-herself affection.

“Scully,” David Duchovny responded in character, somehow managing to mock her just by saying her name.

They were shooting the much-anticipated six-episode revival of “The X-Files,” which begins Sunday, Jan. 24 on Fox, back in Vancouver, where the original series’s first five seasons were filmed. It’s been 14 years since an original episode aired, almost 23 years since the show began. In 1993, the two actors had no idea they were about to start a phenomenon that would propel them to worldwide recognition, demonstrate the power of genre television and mark them, whether they liked it or not, as Mulder and Scully for the rest of their working lives.

“For a very long time, I just could not think about it anymore; I was so ready to be done,” Ms. Anderson said, remembering the grind of doing about 25 episodes a year for nine seasons. Virtually unknown and only 24 years old when she landed the part, she worried for years that the role would swallow her entire career. When the series ended, she moved to England and made a point of taking parts in higher-brow productions such as the BBC adaptation of Charles Dickens’s “Bleak House.”

Only in recent years has the idea of returning to the Scully character seemed enjoyable. “If I was to look at the bell curve of my ego, I would say that it would have been harder at other times to do this series again, had I not proved to myself — and to other people — in the interim that I could do other things,” Ms. Anderson said.

When it first aired, “The X-Files” was not a sure thing. The initial audience (an average of 11 million viewers per episode in the first season) was small but intensely loyal, invested in not only the supernatural stories but also the dynamics of the Scully-Mulder relationship. By its fourth season in 1996-97, the series had exploded into a mainstream hit, 11th in Nielsen ratings and averaging 20 million viewers per episode. (It also spawned two films, “The X-Files” in 1998 and “The X-Files: I Want to Believe” in 2008, the last time they played Mulder and Scully.)

“Without ‘The X-Files,’ you don’t have shows like ‘Lost’ or ‘Heroes’ or even ‘Bones,’” Mr. Duchovny said. “There were all these tributaries that came out of the show, this whole Comic Con-ization of the world.”

He added: “I think it became more than any of us saw, certainly more than I saw. I was not interested in aliens, and that’s what I assumed the show was about. So I was completely wrong.”

Chris Carter, the creator of “The X-Files” and still its driving force, didn’t care much about aliens, either. But he was fascinated by how many other people seemed to be. In the early ’90s, supermarket tabloids like Weekly World News and airport paperbacks like Whitley Strieber’s “Communion” were filled with tales of U.F.O.s and alien abductions. The idea of a show about conspiracies, real and imagined, appealed to him. It took several tries before he could persuade Fox, where Mr. Carter had a development deal, to give the concept a shot.

The underlying premise, Mr. Carter believes, is even more relevant now. “There’s something in the wind right now,” he said in a telephone conversation. “People seem concerned, more than ever, about whether the government is really looking out for their best interest. It’s always been there. But lately it’s ratcheted up.”

The new “X-Files” episodes will touch on matters of high-tech surveillance, cabals, government conspiracies and, yes, U.F.O.s. But, as in the original series, there will also be stand-alone “Monster of the Week” episodes. The one they were shooting this particular day, written and directed by Darin Morgan, is called “Mulder and Scully Meet the Weremonster.”

Mr. Duchovny, 55, and Ms. Anderson, 47, seem more comfortable playing Mulder and Scully than they ever have. Their on-screen chemistry, always obvious, has only increased, and their off-camera relationship has changed. They weren’t really friends when the show began. Now, they tease each other between takes, sometimes breaking into giggles and falling into each other’s arms. When Ms. Anderson botches a line, she lets loose with a barrage of hilariously obscene self-criticism, using words that Dana Scully would never, ever say.

“I think both of us are able to savor things more, to appreciate how lucky we are to have had this experience,” Ms. Anderson said. It had not always been that way. Mr. Duchovny was the one who instigated moving the show’s production from Vancouver to Los Angeles in 1998, partly so he could be better positioned for feature film roles. There were arguments. There were lawsuits. There were days when it wasn’t fun.

“In the beginning, it was a big struggle for him,” Ms. Anderson said, “and there was often a sense that he’d rather be somewhere else.”

By the time the series ended in 2002, Mr. Duchovny, who was only in half the episodes of the final season, was clearly ready to move on. “I wanted to have other things in my life and the show was all-consuming,” he said. “But it wasn’t because I was tired of the character. I always thought I’d play Mulder again.”

And it was Mr. Duchovny who initiated the show’s return, reaching out to Ms. Anderson and Mr. Carter early last year, and once they were on board, approaching executives at Fox.

None of this would have happened, Mr. Carter said, if not for the continued urging of online fans, many of whom are too young to have seen the show in its original run. At Comic-Con 2013, a 20th anniversary “X-Files” panel drew one of the largest, most enthusiastic crowds of the sprawling event.

“I’d actually had very little direct contact with the hard core fan base before that,” Mr. Carter said. “That the show would resonate with them when there’s so much else out there, that it would have a life beyond its original life, I have to say I find it incredible.”

Ms. Anderson, who admits she wasn’t really conscious of the series’s cultural impact while she was working on it, now appreciates Scully in ways she never could before. “There’s a certain quality to the respect and the love that people have for the series and us deciding to do it again,” she said. “It’s different I think than if we’d just done another ‘X-Files’ film. Because people’s relationship with TV is different. There’s such a positivity to it. And a purity. It’s almost like people have been told there’s going to be a second Christmas. And I kind of feel the same way.”