This post contains spoilers for The Twilight Zone Episode 4, “A Traveler.”

Steven Yeun’s Twilight Zone journey began with a D.M. It came from Jordan Peele, asking the actor if he’d like to appear in an episode of Peele’s reimagined Twilight Zone, now airing on CBS All Access. Yeun’s response? “I just said, ‘Oh, hell yeah.’”

Like Kumail Nanjiani, who came aboard before a script for his Twilight Zone episode was even finished, Yeun said in an interview that he agreed to the gig without knowing basically anything else about it. He wound up playing the title character in “A Traveler,” which premiered Thursday—an enigmatic, fedora-wearing character who randomly appears in an Alaskan jail cell on Christmas Eve, asking to be pardoned.

The Twilight Zone executive producer and Monkeypaw Productions president Win Rosenfeld said that they’d had Yeun in mind for this episode from the beginning—and that once Yeun took on the character of A. Traveler, “he actually had a real hand in how that script evolved.” Executive producer Simon Kinberg agreed, saying, “We really looked to the actors to bring as much dimensionality and detail and thought to the characters as we and the writers had. And we’ve gotten great work out of actors. Kumail [Nanjiani] is another perfect example . . . He brought a lot to that character. He wrote a lot of the jokes. He was really precise about the transitions the character was going through in the episode . . . It’s that kind of work [that], because it’s one and done, we need from our actors.”

“We just kind of openly talked about it, which was really cool,” Yeun agreed. “They were so great about letting me have a little input.” Yeun also worked to beef up his character’s mysterious side, in an attempt to make the episode as unpredictable as possible. “It became pretty interesting—just a lot of layers,” Yeun said. “I feel like a lot of things are said without being said.” Glen Morgan, who wrote the episode, gave Yeun a book that also helped him develop his character and performance: The Art of Seduction by Robert Greene. “It really breaks down the different types of people—different types of players that are experts at seducing in that way,” Yeun explained. “That was a really fun read, ’cause that would just kind of change it up, based on who I was talking to or who I was trying to seduce.” The most crucial detail, though—his character’s striking, old-fashioned fedora—was episode director Ana Lily Amirpour’s idea.

Throughout the episode, Yeun toys with everyone in the police station—including Yuka, the deputy played by Marika Sila, and her obnoxious boss, played by Greg Kinnear. Somehow, he knows droves of personal and confidential information about all of them; at the same time, he dances through their office Christmas party with unnerving levity—especially when singing “The Man with the Bag” in a round of Christmas karaoke. Although Yuka’s drunk brother, who is stuck hanging out with Yeun’s character in a nearby jail cell, freaks out relatively early in the episode—claiming he just watched “A. Traveler” transform into some kind of slug—it isn’t until the very end of the episode that we see his true form. Indeed, when viewers finally get a good glimpse at Yeun’s character in non-human form, it appears he’s “traveled” from somewhere . . . very far away.