At one time in adapting Laird Barron’s short story “-30-“ for the new film “They Remain,” writer/director Philip Gelatt considered the possibility of adding another moon to the sky for Keith (William Jackson Harper) and Jessica (Rebecca Henderson), the two scientists sent to explore what life still exists on the remote grounds once populated by a fanatical cult that dabbled in wild experimentation in the not-too-distant future. It is assumed that this is Earth, but its history has made it alien, with the scientists placing heat-sensing surveillance around the forest just outside their base camp to detect potential movement and Jessica certain she can hear someone saying her name. Then there’s also the issue of living in isolation for a seemingly endless mission — as Jessica tells Keith about the whispers she’s been hearing, “The mind gets bored. It will play games. It will act out,” leaving Gelatt to think the actual environment may not need any trickery to get his point across.

“At the end of the day, it felt like too much of a gimmick to make it that much, so instead, we just tried to pick subtle ways to imply a science fiction element without having it be on the moon or having [Jessica] be a robot or those kinds of things,” Gelatt said recently of his second feature as a director. “One of Dario Argento’s movies [“Tenebrae”] he considers to be a science-fiction film. It’s not at all. but I always thought that was so funny that now any time I write something, it’s like ‘Yeah, it’s just a little bit science-fictiony, like that Argento movie.’”

The fact that you can’t exactly place “They Remain,” either in setting or by genre, all boost its considerable intrigue. Boasting strong performances by Harper and Henderson as the pair dispatched by a mysterious corporation to collect DNA samples in the area, the tense two-hander finds that there’s as much unknown territory to explore between the scientists in conversation as there is outside their tents as their dates for a return home are continually delayed and the information they receive from their superiors about their mission is specious. Although the two come to rely on each other more and more, Keith and Jessica feel increasingly alone as “They Remain” wears on, becoming distrustful of even their own impulses, which are already quite different from one another and Gelatt mines the ever-widening gap between what they’re experiencing and how they behave to ask how an environment that is both verdant and yet dismissed for dead with no other human life on it has slowly seeped into their system.

Whether it’s horror, sci-fi or simply a creepy human drama, “They Remain” efficiently gets under the skin and after premiering last fall at the H.P. Lovecraft Film Festival in Portland, Oregon, where it was right at home in terms of its influences, the film begins its national theatrical run this week and Gelatt was kind enough to speak to creating a film of great ambition with both a limited location and budget, as well as taking an unconventional approach to casting and having the production be at the whims of the local weather.

William Jackson Harper in "They Remain"How did this come about?

I was a fan of Laird’s work and when I was looking for something to write and direct, I started going through his work and found the short story it’s based on called “-30-“. I loved how strange and mysterious it was and it felt like both something I could do and it would also be something that was a challenge to do, and that just felt like something I had to try. So I sent it to my producers and they may have been slightly more skeptical about the material than I was, but they liked it and I was very gung ho about it being something that should be made, so we proceeded from there.

It sounds like you wanted to make something you could produce easily while not skimping on the ambition of it. You obviously pulled it off, but is that easier said than done?

The short story is set in the high desert and I knew we probably didn’t have the budget to move our production to shoot on the West Coast, so one of our producers has a piece of land in upstate New York, and one of the early considerations was could we should on this piece of land and visually do what we wanted to do. We took a couple trips up there and did early scouts of the land and figured out that we could, so that was a big piece, knowing that there was this piece of land that would suit us. Then from there out, we did not have a huge budget, but we tried to be very conscientious in how we spent it, so we did build those domes, or I call them domes — those strange structures that the scientists work in, so that was a bit of an expense. But everything else we tried to keep as lo-fi and doable as we could and lean into making the style of the movie stand out.

For lack of a better term, those domes are so striking both during the day and at night. How did you come up with them?

We didn’t design them. They’re supposed to be emergency shelter [that] you’re supposed to drop into war zones and people build them to live in and this insane person in the Pacific Northwest actually has this company [that creates them]. When I say they’re designed by a crazy person, I mean a crazy person — we bought three of them and when they were delivered, they weren’t delivered [already] built and it comes with a 200-page instruction manual that is befuddling — it’s like a Lovecraftian text. [laughs] It was about two tons of flat plastic and then you basically origami’d them together. It’s so hard [to build] and the idea that you’d drop these into war zones is so sadistic, I can’t imagine them being parachuted in. Our art department basically built the platform that they’re on and figured out how to connect them so they have the kind of odd sci-fi look about them, but they showed up on set [which] was off of a dirt road, and this enormous semi drove down the dirt road and the driver opened the back of the truck and there was just a ton-plus of plastic back there. It was absurd. But it looked cool, so what can you do? Anything for the movie, right?

Rebecca Henderson in "They Remain"One of the things I’ve admired so far about your work so far in both this film and “Europa Report,” which you wrote, is the way you create a future that doesn’t omit the past – there are rough edges and a bluntness to the language at times that lacks the polish most films set in the future have. Is that difficult to figure out what you want to keep and what to discard about the present?

It’s tricky. One of the things I appreciate most in movies is subtlety, but in a movie like this and everything that I do, trying to figure out that line of how subtle is too subtle, what you have to be upfront about with the audience and what are you able to pull back from and are able to let them intuit on their own is always really hard. My feeling was I should make the script and shoot things to be as explicit as possible and then pull back in the edit room to get the subtle effect that I wanted, so in the script and in early cuts of this movie, there are scenes [where] people are saying things a lot more bluntly than [it is now] [laughs] and then I cut it back to try to get after what you’re saying, [where] it’s kind of today, but it’s kind of not today. It’s kind of the future, but it’s kind of not, which is a tone I always love.

How did you find your leads to help pull that off?

When we were casting, we sent the script out to agencies, but I don’t love the audition process because it feels like an actor comes in, [it feels] like they’re in front of a firing squad. So instead of doing auditions, we brought prospective actors in and had a conversation with them about the script, the story and the characters and one of my questions was basically just what happens in the story – like tell me the story in your own words, so I was curious what they would’ve seen in it and what interpretations they might bring to it. I’m a very big believer in moviemaking being a highly collaborative process, so I wanted actors that I felt would bring ideas and we could discuss things. Both Rebecca and Will were great in those meetings and had engaged with the material and had smart takes on it and there was something intrinsic in who they were that felt like these characters to me, which was great. By design, we didn’t really do any [rehearsals]. I knew that they knew each other a little bit, but I also wanted to just drop them in and start shooting with them to replicate the way the characters are working with each other, like they’re just sent [to this place] and forced to figure it out.

William Jackson Harper in "They Remain"Since so much of the film is outdoors and you get those extraordinary landscape shots, did the weather actually cooperate?

Let me tell you a story about being a dumb director…[laughs] I was like, “Yeah, we’re going to shoot in the woods and whatever the weather is, that will be the weather for the scene. It’ll be fine.” That’s a very cool, brazen thing to say, but also quite stupid. It is not easy to shoot outdoors. We had windy days, we had rainy days, we had freezing cold days. You can see a little bit in a couple of shots that we shot in the fall, but it started to frost and there were mornings that were just bitterly cold. There are a couple of scenes that are in the rain outdoors, and we ended up mutating our schedule a little bit to deal with that and it’s not easy to shoot in that dome when it rains because of sound, so whenever it rained, it would just become miserable. I think we have a [picture] on Instagram of a grip trying to hoist a tarp over the dome when it’s raining and he looks like a sailor trying to like navigate a typhoon. [laughs]

With a limited location, you make the film quite dynamic through the shot selection. What was it like figuring out how to never have the same shot twice?

That was also really hard. Those domes are hard to shoot in. Those walls don’t move, so once you’re in there with a crew, there’s not a lot of room to move around and it became hard to pull off what you’re saying, but I definitely wanted to because the risk with a movie like this is that everything starts to feel the same and it starts to get visually boring. So there was a lot of work between me, the DP [Sean Kirby] and the actors to try and figure out how we could block a scene differently, how we could get the actors to move differently. We do replicate some [camera] set-ups, but even in set-ups that we repeat, you try to bring something a little bit different each time and light it a little bit differently to make sure your big glowing white dome looks a little bit different every time you’re seeing it. It was a fun challenge.

William Jackson Harper in "They Remain"The score is quite unsettling. Did you have strong ideas about it from the start?

Before we even shot, I gave the script and the story to our composer Tom Keohane, who’s amazingly talented, and I said, “Here’s the story. Make some music for me based on this story.” So he did a couple pieces before we shot anything and some of that music is actually in the movie. Then after we shot, there was like an ongoing debate about how science fictiony the score should be, so Tom actually did some pieces that are like you’re coming into neo-Los Angeles [in] “Blade Runner” [where] the movie started with a sweeping, synthy piece of music, which is amazing, but it set the wrong tone. You expected [Jessica] to be a robot. It just didn’t feel right. So we pulled back on that, but kept a little bit of it and then had Tom explore different sonic landscapes. There’s the culty/chant-y music [that] I was really into [to compliment the landscape] and most of the voices you hear are actually his voice, just modulated different ways to get that strange culty singing. He did such a fantastic job and I think we made the right decision not to go with the “Blade Runner” stuff. It was definitely cool, but not quite right.

What’s it been like traveling with this?

You don’t set out to make a movie like this thinking it’s going to be a huge crowdpleaser, so it’s exciting to let people experience it and to react to it, whether they love it or hate it. It’s definitely a movie for a certain type of audience and the response has been overall pretty good. We were at the Lovecraft Festival in Portland and the reception there was great, and [the Panic Fest] in Kansas City [where] people seemed to really like it as well, so I’m pretty pleased.

“They Remain” opens on March 2nd in New York at the Village East Cinema and on March 9th in New York at the Laemmle Music Hall.