Even though it's only January, we're calling it now: Starz's Counterpart is one of the best television series of 2018. Despite being set in the present, Counterpart has a Cold War vibe that chills to the bone, and its spy-jinx are so subtle that the plot doesn't happen as much as creep up on you. It's just plain terrific.

WARNING! Spoilers for the first episode of Counterpart lurk in the shadows below!

Executive producer and writer Justin Marks spoke to SYFY WIRE about his show and the people therein, many of whom have more than one version of themselves—the character and their alternate "Prime" version. The show's elevator pitch is: "It's about a man [J.K. Simmons] who meets his alternate self." But in truth, it's "about" a great many things, including identity, roads not taken, spy games, assassinations, and what happens when everything you thought you knew—about your world and even your spouse—was wrong.

You say you were inspired by spy fiction from writers like John LeCarre as much as science fiction. How is this reflected in Counterpart?

Justin Marks: My favorite kind of genre is the kind that tricks you into realizing it's even genre to begin with. We [try] to not to take from the tropes of science fiction, which I love, but to take from the tropes of the spy genre—the Cold War spy genre, specifically.

One of my favorite science fiction movies of the last ten years is Children of Men, which is a movie that completely conceived of its world, and instead of turning on the overhead lights and saying here it all is, they just hand you a flashlight and say go around and look at all the details and paint a bigger picture from there.

That's what we try to do. We slowly build this science fiction world that evolves and blooms as the season goes. But by that point, we understand the characters and we understand what these human stakes are.

So you're de-emphasizing the backstory and emphasizing the characters?

I think this is a show about lonely people. When you put a lonely person in a room with another version of himself, in some ways they feel more lonely than they ever did before.

The show ultimately is a portrait of a marriage. And it's two marriages in some sense, two versions of the same marriage [between Howard and Emily, between Howard Prime and Emily Prime], so it creates for itself a bit of a love rectangle.

Is it a challenge for the actors to play two different versions of the same character?

[J.K. Simmons] would shoot one version as himself… and [when] he would then change to do the other Howard, he wouldn't just put on different clothes and come back. He would remove all of it, take a shower, and go through a whole process, because he had to dress as the other character to know how the other person dresses. Because one Howard may dress this way, the other Howard dresses this way, and this was his way of finding each person before he showed up.

He walks differently and he acts differently. Howard [Prime] is two inches taller. I don't know if you noticed that, which we didn't do for visual effect. [Howard] is just slouched.

There's this crucial, devastating scene in the third episode. He did this performance and this moment as Howard Prime, and afterward, I said to him, "At that moment of vulnerability, which is for Howard Prime a really hard thing to do, I saw Howard. Was Howard there?" And he looked at me, and he's like, "Oh yeah, I guess he was." He had no idea because he's an inside-out kind of actor.

Video of Counterpart | Official Trailer | STARZ

How are the two worlds different?

There are ways the other side is very different from our world, you kind of get a glimpse of it in the first episode, and there's one key thing that begins to become apparent that spells why these people are so different, but it's fun not to just spoil that in the first episode, let that grow as the show takes on its own life.

We have very subtle distinctions in the way these two worlds look, whether it's the cell phones or certain rules that we have about what kinds of periodicals are left out and what kinds are not. We built it down to a granular detail, hopefully without calling too much attention to it, because I want to reward people who are paying attention to it. I think a lot of clues as to what the other side is like are buried in that.

One of the things, the "interface room" we call it, that long line, that was a specific choice. It was because if you notice there are two things that are very antiquated there, the gender division and technology are still both sort of rooted in a time that might give clues as to when the Crossing first began, and the fact that it's sort of frozen in a certain version of that culture.

So what makes the two Howards so very different?

There are ways the other side is very different from our world. You kind of get a glimpse of it in the first episode. There's one key thing that begins to become apparent that spells why these people are so different, but I won't spoil that either.

We have these kind of really fun therapy session conversations [in the predominantly female writers' room] that go into the nature vs. nurture question, and who would I be under a different set of circumstances, and where would we go? We tend to take a very fluid interpretation of what makes us who we are, that under a different set of circumstances, I could be very different. But am I always bound by a rubber band or a magnet that pulls me back to a certain center? And where is the center?

You've worked in film before, on The Jungle Book, as well as the upcoming Top Gun: Maverick. What made you decide to transition to television?

It came from this project. This is a very personal story to me. In Howard, there's a lot of my grandfather, who worked the Treasury Department for his whole life. I wanted to tell a story about that version of him and how that became me in the end. I knew that two hours was not going to suffice. It was just a question of finding a partner who would support that. Fortunately in Starz and MRC [Media Rights Capital], we had people who were willing to do this for two seasons right from the get-go and give me time to build the show.

In what other way is Counterpart personal to you?

My wife watches scenes and characters between her fingers, because she knows where stuff comes from. That story of when [Emily] got up to wash up and [Howard] said to the waiter, "I'm going to marry her?" -- that's what I said to the sushi chef on our first date.

(This conversation has been lightly edited.)