Genre icon Curtis Armstrong is about to make his debut on Frequency, and the introduction of his character will leave The CW’s remake of the film for TV forever changed.

In Wednesday nnight’s episode, “Deviation,” Raimy (Peyton List) meets a strange character named Karl (Armstrong), who claims that—just like her with her ham radio that contacts her father Frank (Riley Smith) in 1996—he speaks to himself in the future with his own communication device. The wrinkle: he’s in jail for murder because he claims his future self told him to kill his victim for the greater good. Does Raimy believe this convicted killer, or will she just consider him a lying, desperate man trying to be released from prison?

“He’s so good,” List told Nerdist on set in Vancouver about having Armstrong (Revenge of the NerdsSupernatural) on the show. “I remember we had one day where he had a lot to say and it was kind of a treat for me because I just got to sit back and watch him. He made so many brilliant and interesting choices and I just felt kind of spoiled. It was a really fun day of work actually. Maybe not as fun for him, he had to talk a lot, but it was really, really cool.”

While Armstrong is only a guest star on the show, his presence as Karl will affect Raimy’s own understanding of the timeline and how her ham radio works on a very important level.

“I think a lot of times, with Raimy and with Frank, dealing with the idea of the ham radio and what it allows them to do, they’re forced into a lot of situations where they can go down so many different roads with it and they kind of have to prioritize, to a certain degree, where you take in so much information,” List says. “Where you go, ‘You know what? If that’s not pertinent right now, throw it out, move it along.’ He does float that idea of, ‘How do you know you’re not the only one?’”

She continues, “I think, for them, they’re going, ‘I just can’t think about that right now because we haven’t even begun to figure out how to control the situation that we need to control. That is something we can’t control. We’re not gonna worry about it right now.’ But is a very interesting sort of wrench to throw in because, all of sudden, if you have other people messing with the timeline, it’s a bit of a problem.”

On a personal front, Raimy is going to continue to pursue her former fiance Daniel (Daniel Bonjour) in this new 2016 timeline where he doesn’t have any memory of their relationship, even though she has a new love interest forming in Kyle (Rob Mayes).

“It’s interesting because this other love interest is a surprise to her,” List says. “She doesn’t even remember it until she remembers it in the most embarrassing way possible. What’s been interesting to me, taking on those episodes with the Daniel character, is remembering to forget the life that they had together because that life will never come back. It’s gone forever. She can remember all of those wonderful memories she shared with him, but there’s no way [she can get that back]. You can’t reset to exactly where you started.”

She continues, “For me, it’s been hard to be like, ‘Okay, that’s completely gone.’ And there’s no throwbacks to those times because he’ll have no idea what she’s talking about. They’re very different, those relationships, and I think that she’s a different person, or a different woman, with either one of them. That’s an interesting dilemma for her because she was absolutely 100 percent certain when she was with Daniel in our original timeline, and throwing in somebody else, all of a sudden she’s questioning things she never questioned before. But, then again, she has to start her relationship with Daniel all over again.”

Because of the fact that Daniel has no memory of their original relationship, that means that Raimy has to hold back “a lot” in their new relationship for fear of scaring him off.

“She’s already terrified him,” List says with a laugh, noting that she has basically been “stalking him” in the new timeline. “At a certain point, you just realize it doesn’t matter how many times I tell you that we’re perfect for each other, you won’t know until you feel that. So, I think she holds back a little bit, as to not come off crazy and say all these outrageous things, but, at the same time, there’s this part of him that always brings out this side of her that’s a little bit less guarded and a little bit more relaxed and herself. And I think she still has that.”