Let Chris Carter explain.

On Monday, the X-Files revival welcomes a few fan-favorite characters from the original series. Surely you recall Byers, Langly, and Frohike, the conspiracy nuts collectively known as the Lone Gunmen? The trio proved so popular with fans of the original show that they actually got their own short-lived spin-off series, The Lone Gunmen. After the show’s cancellation, the characters returned in a season 9 episode of The X-Files. And … well, they died.

So, how it is possible that Bruce Harwood, Tom Braidwood, and Dean Haglund are back on The X-Files in Monday’s episode? And why do they appear to be competing in a Gene Autry cosplay contest? “When you’re dead on the X-Files, you’re never necessarily gone,” says X-Files creator Chris Carter, who wrote and directed Monday’s episode. “There are ways to bring people back in dream sequences, flashbacks, and the like. This was an opportunity to use them, and bring them back to the show, in what is a presumed psychedelic hallucination.”

Did Carter ever regret killing off the Lone Gunmen in the original series? “We just did what the network did [to] their show: Pull the plug!” Carter laughs. “I was sad to see them go. They were go-to characters when you needed weird exposition. I didn’t want to pretend that they weren’t dead, but I was looking for any way to bring them back.”

Monday’s episode is called “Babylon,” and features an appearance by another key X-Files figure, plus guest stars Lauren Ambros and Robbie Amell. To find out more about the episode, come back to EW.com on Monday morning for more of our exclusive chat with Chris Carter.