The actor talks with THR about how Sunday's season-one ender set the stage for what's to come next.

[This story contains spoilers from the season-one finale of Starz's Counterpart.]

Starz wrapped the first season of its critically praised spy-fi drama Counterpart on Sunday with two shocking deaths and the cold war between the parallel worlds suddenly getting a whole lot hotter. At the center of it all were the two Howard Silks — the super spy and his meek doppelganger, both played by series star J.K. Simmons.

During the hour, Howard Alpha — desperate to go back to his world — meets with Alexander Pope (Stephen Rea) to beg for his help. Pope offers to assist in getting him back to our Earth, but only if Howard becomes his assassin on the other side. Howard then tells Pope he is nothing like Howard Prime, and never will be. Pope pulls out a gun and forces Howard Alpha to kill him in self-defense, marking the first time Howard Alpha has ever killed a man.

Meanwhile on our side, head of housekeeping Aldrich (Ulrich Thomsen) forces Howard Prime out of hiding by leaving his comatose wife, Emily (Olivia Williams), unguarded at the hospital. Howard Prime rushes to her bedside, thwarting another assassination attempt by Baldwin (Sara Serraiocco). Instead of killing Baldwin, Howard Prime pays her off to walk away. Aldrich and his team descend on the hospital with the intention of killing both Howard Prime and Baldwin. Just as Aldrich is set to kill Howard Prime, Baldwin emerges from the shadows and kills Aldrich, as payback for the murder of her doppelganger. With their ledgers now balanced, Howard and Baldwin part ways.

The season ends with a deadly terrorist attack on the Office of Interchange headquarters, creating a diplomatic emergency that closes the bridge between the two universes, stranding the Howards in each other’s strange new world.

Below, Simmons talks with The Hollywood Reporter about the deadly season-one finale and what's next for the Starz drama.

What initially attracted you to Counterpart? Was it the opportunity to tackle a dual role?

I read the script. I had no idea that there was a dual identity thing until page 20 when it's first revealed in the story. I was very drawn to Howard and his place in this sad Fritz Lang-like dystopian world. When the black hood comes off of the other Howard, I was completely surprised. Once I finished the script, I immediately read it again from the other Howard’s point of view. I thought he was just a simple, kind, gentle, sad-sack protagonist I was playing and then when the other character came along, it's twice as interesting and twice as much work and twice the intrigue for the audience, especially as more characters end up dealing with their counterparts.

The scene in the interface room where the two Howards face off gets pretty heated. It also seemed like Howard Prime, for the first time, shows a little vulnerability because he's feeling threatened.

That was the time when you not only see significant vulnerability from Howard Prime, but also see our original Howard growing more of a spine. We really see both of them beginning to take on aspects of each other.

The scene in the finale that was so shocking is when Howard Alpha kills Alexander Pope. That's the first person he's ever killed, so that would have to have a major impact on him.

Absolutely. One of the nice things about this show is this sense of collaboration, with [creator/showrunner] Justin Marks. He had written a version that made Howard just a murderer. I thought it was important — because Howard's overall thematic arc in the first season is that he becomes Howard Prime and I was somewhat resistant to going all the way with that. Howard Prime is an ethical character in most ways. So, it was important to me that that would be a moment of a gut reaction and self-defense. Was there anger in it? Yes. But he really was kill or be killed in that moment. And maybe the Howard that we met in the first episode might not have had the cajones to come out on top in that confrontation. That was the interesting evolution of that character. I'm glad it’s that shocking moment. The bad part is I seem to be done having scenes with Stephen Rea and those were fun, especially since I was a spectator half the time because Stephen was carrying most of the dialogue.

We haven't seen Stephen Rea as Alexander Pope on the Alpha side, so he may still be around.

This is always a possibility until they kill you twice.

Have you been given a backstory about what got Howard Prime to this point? Will there be flashbacks in season two that show as much?

We are seeing some flashbacks and we're also investigating the past in dialogue as well in season two. But that was another thing that Justin and I spoke about the first time we met: where was this point of divergence? Is there a single thing that we can really point to as to why these guys started going in different directions? We definitely fill in some of those blanks in season two. I've only seen the first five scripts of our second season so far. The hope is we're doing this show for five, six, seven years. That said, we're not going to tie everything up in a neat little bow at the end of season two, either. There will still be things to investigate.

Betty Gabriel is joining the cast for season two, playing Naya, a former FBI agent brought into OI to clean house. Have you had the chance work with her yet?

I had lunch with her. I was very excited to have her join us. Like a lot of people, I just became aware of her as a result of Get Out and she was just absolutely brilliant. She is going to be with us for a while. As one of the Howards, I get to work with her a fair amount and we'll see what happens in the second half of the season.

She's being brought in as a cleaner, but it it's unclear if she's from the Alpha side or the Prime side.

I can't say anything; I don't want to get my hand slapped.

What did you think of the Counterpart season finale? Sound off in the comments section, below. Click here to read our deep dive into the finale and what's next with creator Justin Marks.