If you’ve kept up on prestige television during the last decade and a half, there’s a good chance that at some point your favorite series had Graham Yost’s name in the credits. Since 2010, Yost has served as a writer and/or producer for such acclaimed shows as “The Pacific,” “Masters of the Air,” “Slow Horses,” “Falling Skies,” and both the original run of “Justified” and the recent “Justified: City Primeval.”

Currently, Yost’s full attention belongs to Apple TV+’s “Silo,” which Yost produces and serves as the series’ showrunner. The hit science fiction series is adapted from a trilogy of novels by Hugh Howey. Set in a dystopian future in which humanity lives in a massive underground bunker, the acclaimed series stars Rebecca Ferguson as an engineer who’s obsessed with learning the truth about the outside world — a quest that sets her on a collision course with the authoritarian leaders of the Silo, who would prefer to keep everyone in the dark about what’s really happening.

An incredible ensemble of Rashida Jones, David Oyelowo, Common, and Oscar winner Tim Robbins surrounds Ferguson’s Juliette. Morten Tyldum, the Oscar-nominated director of The Imitation Game, directed “Silo’s” first three episodes.

The result is an engrossing series that expertly blends sci-fi thrills with mystery and apocalyptic unease, but per Yost, it wasn’t always an easy balance to strike. He highlights the pressure of adding more excitement to suspense setpieces while infusing the story with a sort of Scandinavian gloom, as well as figuring out how much to tease the show’s big reveals.

“In this streaming world, the writer’s room has to produce all ten scripts for the season,” Yost explains. “So we block shoot the whole thing, which means we got time with all the scripts, and we could go through and say, ‘Where do we mention the tape? Is it enough? Is it too much?’”

Awards Focus spoke to Yost about the unpredictable chemistry between actors, peppering the season-long IT tape twist into the early scripts, and what was going through Juliette’s head in the final moments of the finale.

Awards Focus:  The driving force for Juliette (Rebecca Ferguson) to figure out what happened with her lover and leading her to this mystery which sends her outside the Silo…. those closing moments were electric. Was that always the planned close to season one?

Graham Yost: We said, “What a great season-ender it would be, her going out and over the hill and disappearing.” But her relationship being a driving force for her character wasn’t in the book like that, it was brief, and we needed to make a bigger deal of that. We need to see her slowly unraveling the mystery, because we had to fill ten hours.

AF: The setpieces that you’ve designed, especially fixing the turbines in the engine room, they were just electric. It goes back to reflecting humanity in the characters and their faults, their fears… specifically, one of the guys working with Juliette doesn’t think he can get the job done and he’s fumbling in fear. It adds beautiful tension to that ticking clock. Can you talk about how you orchestrated that?

Yost: A lot of that was the director saying, “Could we add something? Can we say she’s afraid of water? Can we add something where she has to go into the water?” We know she’s not going to die, because it’s Rebecca Ferguson, and she’s the face on the poster. But can we put her in harm’s way?

Also, Aric Avelino, who wrote Episode 106, was on the set. I’m 8,000 miles away from the set, so I didn’t get out there all the time. Aric worked it out with Morten (Tyldum), it doesn’t make perfect scientific engineering sense, but it’s fun. Everything has some level of a three act structure. What’s the problem? When does the problem get worse? When does it look like they’re not going to survive? And what’s the solution? We built it around that.

AF: I love Tim Robbins’ character’s focus on the tape and how that comes into play perfectly at the close of the season. Was that thread something that you had early on, and you knew it was going to be a huge “ah-ha” moment?

Yost: We debated that, and we went over all the scripts. Did we mention the tape enough, did we mention it too much? Is there a way we can have it mentioned but make sure it’s buried? “Not like that shitty IT tape,” — we hear that a few times.

Then the character of Walker puts it together and figures out what’s really going on with the tape. In this streaming world, the writer’s room has to produce all 10 scripts for the season long before we actually start filming the season. Especially with Silo because we have certain sets that have to be repurposed and changed into other sets.

So we block shoot the whole thing, which means we got time with all the scripts, and we could go through and say, “Where do we mention the tape? Is it enough? Is it too much?” When I see it now, I go, “Oh, God, we’re mentioning the damn tape again.”

AF: When it came to score, Atli Örvarsson said that Morton had mentioned this project to him. What was your first encounter with him?

Yost: I trusted Morten on this, as he’d worked with Atli on Defending Jacob and knew that he could deliver great stuff. Then I met him, and he’s such a funny, easy-going guy. He’s a professional, and he loves doing the work. None of us love getting notes, but he’ll take notes and say, “Okay, I’ll try it this way.”

There were times where we were running out of time, and we said “Okay, Atli, we need a big theme for the end.” And he said, “Okay, I’ll come up with something.” We trust him, and he does a great job.

One thing Morten than I totally agreed on is we wanted something slightly Scandinavian, only in intent, not really in sound. There’s something slightly melancholic about it, because everything that Juliette is going through has an aura of melancholy. She formed an alliance with the sheriff, and then he goes out to clean and dies. Her boyfriend is dead. She doesn’t know why or what happened.

The history of her mother, her estrangement from her father. There’s a certain amount of Nordic weight on her shoulders. Rebecca is Swedish, so she knows that very well. Atli nailed that tone, and it can go romantic when it needs to, and it can go incredibly cool with the action as well.

AF:  The casting is just so well done with this — Rebecca’s relationship with her father and that strain between them. Could you imagine that those two actors would be that electric on screen?

Yost: You don’t know for sure. But you do know there’s a certain level of professionalism and the right attitude, and you pick that up on the Zoom. I knew that it was going to be a joy to work with Rebecca, and it has been. We get a kick out of seeing each other when we get together, make each other laugh and talk about real stuff about our lives.

And then there’s the work, so I knew she would be a really good partner. Meeting Iain Glen and Zooming with him, I was like, “Oh, yeah, he’s the guy.” Then you hear reports back, Rebecca texting, “Just did a day with Iain Glen. Oh my God, what a treasure.” And I talked to Ian, and he said, “It’s so much fun to work with Rebecca.” All of that, you don’t know. You’re going on their professionalism, the work they’ve done, and you hope for the best. You know that it’s going to be good. You just never know for sure if it’s going to be great. In this case, they ended up being absolutely wonderful together.

Iain Glen in “Silo,” courtesy of Apple TV+.

AF: Sci-fi is a great genre and it doesn’t get enough opportunities in the media to be done well. When you go to Apple, do they trust you based on your historic career?

Yost: There’s a certain level of trust between me and Zach and Jamie at Apple. Also (a trust) between Morten and them, because he’d done “Defending Jacob” and they really liked it. When we were deciding who would direct “Silo,” they suggested him. Apple has certain things that they need out of casting. They wanted someone high-profile to play Juliette, they wanted someone high profile to play Bernard and Sims. They trust us, but that doesn’t mean they don’t have their ideas. For example, on “Slow Horses,” I never even thought of Gary Oldman. That came from Apple.

The other thing is working with Cami Patton, who was our US casting director. I’ve worked with her since “Band of Brothers.” We did “Boomtown” and all the years of “Justified” together. She was the one who sent in the tape when casting for the part of Mags Bennett. She said, “We really think it’s Margo Martindale.” And how right was she? So when she called me up and said, “What do you think about Common for this part?” I said, “That sounds fantastic.” And then they backed us.

AF: In the finale, we have Juliette in the space suit being sent outside, but this time the suit is sealed properly with quality tape. Can you describe what was going through Juliette’s mind as she exits the Silo and finds the real outside world?

Yost: This is from the books, and I encourage everyone to buy the books, but don’t read them until the series is over. As we get into it in season one, Juliette figures out the display is a lie, but it’s the display inside the helmet. She doesn’t know what that means, she just knows she’s seen those birds flying in that exact same formation. And if you take that further, you realize that maybe they put that in the helmet for people to see, so they’ll think: “People aren’t seeing it because the lens isn’t clean. I need to go clean to make sure that they can see how beautiful it is.”

We’ve been lied to… no one’s dying on the hill, I can get over the hill. But she figures out they die. But she’s got good tape, she’s got a shot. That’s her memory of Walker and the little note she got which is, “We’re good in supply, and I’ve got good mechanical tape, not the shitty IT tape. I’ll go as far as I can.”

So she goes up over the hill, looks back and keeps on going. That’s the basic logic of it. One of the things that I loved about the books was there’s more to the story. But don’t read the books, watch the series, then read the books.

Silo is currently streaming on Apple TV+ and eligible in all voting categories.