Spoiler alert! Do not read further if you haven't watched the season premiere of The X-Files.

The first episode of The X-Files' reboot ended with a familiar sentiment—and a familiar face.

"We have a small problem: They've reopened the X-Files," the Cigarette-Smoking Man (William B. Davis) tells an associate.

And though the X-Files were reopened (and shut back down) multiple times during the franchise's 22-plus years, when viewers last saw the Smoking Man he was very much presumed dead. After multiple fake deaths, CSM's hideaway was bombed in the 2002 series finale—not only was he engulfed in flames, but his skin was shown burning off his face until his skull was exposed.

“I thought it was final [in the series finale]," Davis laughs. "Oh, yeah. But I thought it was final for every death.”

In many ways, it's hard to fathom The X-Files without Cigarette-Smoking Man. He first appeared in the pilot (in the final scene of that episode, too), remaining a mysterious force in the early years. As the series went along, it was revealed that he, along with the members of the Syndicate—a shadow organization consisting of powerful figures—worked to keep Mulder (David Duchovny) and Scully (Gillian Anderson) in the dark about the overarching government conspiracy, aliens and various X-Files-related things. And to make things even more complicated, it was revealed later in the series that he's also Mulder's biological father.

But given how CSM appeared to die in the original series finale, Davis was understandably skeptical about his return. “‘How have you managed this? What would the function of the character be?’” he recalls asking. "[But] I was delighted to be involved. One doesn’t get to play a villain of that sort, that often…a character with that desperation and fearsome commitment to what he needs to do. That ruthlessness, I guess. So it connected with me.”

Originally, Davis' return was intended to be kept quiet, but it didn't last long. Davis quickly became part of the promotional material, and the only level of secrecy was his name not appearing in the episode, titled "My Struggle," until the end credits. "I know [series creator] Chris [Carter] has been kind of convoluted about it, because he was trying to keep me secret," Davis says. "And then all of a sudden, I’m in the publicity. We didn’t do any billing of me in the first episode, and we talked about that, because we didn’t want [fans] to anticipate my being there.”

As for what CSM is up to this time, Davis is mum. “Be patient," he says. "It will reveal itself. But it doesn’t really until Episode 6.”

While he tees up his top-secret plan, Mulder (David Duchovny) and Scully (Gillian Anderson) are now set to start back on the X-Files. Scully, notably, had been reluctant to return to that world in the 2008 film, I Want to Believe, but with the reveal in the premiere that she has alien DNA, things have shifted. “She must be willing to a certain degree, because she shows up," Anderson notes. "But I’m not sure we really deal with that [reluctance], really. We don’t show her process of deciding she’s going to do it again other than that moment you see in the first episode.”

And though Scully was the skeptic for much of the original show's run, she also saw—and experienced—a number of things which shaped her. So while she won't be as open to the supernatural ideas as Mulder tends to be, Carter acknowledges she isn't in quite as much denial about what's going on.

“She’s seen too much," Carter says. "There are certain things she can’t deny—the implant—and certain things that have happened to her which make her believe in a conspiracy; she’s still not sure exactly what to think of that."

“It’s really sort of a feel thing [of how skeptical she should be]," he continues. "Because it’s in my DNA, I have an instinct for how she would react to anything, in any situation. But I think all the writers do, to an extent. No one ever imagined the show would go nine years, 202 episodes. When you have a skeptic and a believer, they’re going to change over time.”

One of the things that will challenge both Mulder and Scully in the second hour of the revival (airing in its normal Monday at 8/7c slot on Fox) is their son, William. Though the former couple has settled into a comfortable work rapport, the grief over losing their son—Scully gave William up for adoption when he was a baby to protect him—rears its head while they're working a case.

“It’s a big part of the emotional arcs for these characters," Carter says. "We learn how they feel in ways we haven’t seen before. What’s interesting is the passage of time, their feelings have changed; they’ve grown and deepened.”

The loss is a different one for Mulder: he was only able to be with his son for a few days of his life. Mulder's life was quickly in danger and he had to flee to keep Scully and their child safe. (Which coincided with Duchovny leaving the Fox series after the eighth season.)

“It’s more of a storyline that was played through Gillian’s character this year," Duchovny allows. "There was a lot of focus from her character on the William stuff, and I think as her partner, ex-partner, the father—maybe, who knows?—of the child, I’m sympathetic and in pain as well, but it was more of a story for Scully.”

“She’s emotional," Anderson adds. "There’s a lot of thoughts and feelings and conversations about it—the choices that they have made, and the impact that has on their lives today. It’s a big theme.”