Director-producer Aaron Moorhead and writer-producer Justin Benson were just about to begin their third micro-budget, mind-bending horror film when Benson’s mother, Randalyn, took her own life.

That third film was The Endless: a sly, disturbing story about two brothers – played by Moorhead and Benson – returning to the possible suicide cult they escaped as teenagers.

It was an awful coincidence. But it also showed the profound, humanist approach of their style of horror: when they pressed on with the film, it was able to meet their grief.

The duo are in a headily enthusiastic mood the night after The Endless’s first UK screening. Benson is bearded with wide, searching eyes, Moorhead the eerie spitting image of Matthew Modine in his Full Metal Jacket-starring youth. But mention of his recent trauma jolts Benson for a second.

Justin Benson and Aaron Moorhead hope to emulate the Coen brothers’ success (Arrow Films)

“There is nothing autobiographical in the script,” he says with consideration. “There is nothing that we were trying to communicate about our own relationship at any point.

“But my mum took her own life three days before shooting. So when you watch the performances, there is a layer of something happening, and it was literally grief. It’s an interesting tuning fork in the movie, in that we were both dealing with that. It’s very interesting.”

The Endless’s cult scenario and bare-bones budget meant cast and crew shared cabins in California’s Anza-Borrego desert, a helpfully communal experience.

“His dad was also the caterer on the film,” says Moorhead. “And so they were able to go through the grieving together. It’s great to watch the film now, because it’s in some ways a monument – and also, it was therapy.”

‘The Endless’ was shot on a bare-bones budget (Arrow Films)

Like their previous work, Resolution (2012) and Spring (2014), The Endless has little interest in following horror rules and expectations, the mechanics which are often deemed to make genre work inferior.

Other genre-bending horror movies such as Get Out, A Quiet Place and Hereditary have recently shown that films with not only visceral but also intellectual and emotional jolts are the way to break the mega-franchise hold on cinema audiences.

Moorhead and Benson are interested in doing things differently. They’re of the post-slacker, post-punk horror generation, signalled by the landmark anthology V/H/S (2012), where improvisational, naturalistic indie mumblecore met ruthless violence (the duo’s bonkers skaters vs zombies story “Bonestorm” ended the last, and worst, sequel V/H/S: Viral).

Ti West’s segment “Second Honeymoon”, in which the exposed intimacy of a sleeping couple’s motel room becomes the nightmare extreme of their daytime deteriorating marriage, defined the possibilities of the horror genre for a generation of filmmakers including Joe Swanberg and Adam Wingard. You could include Ben Wheatley in the bracket too: his Kill List (2011) was as original in its vicious rows over hotel business breakfasts, domestically ordinary hitmen, and upsettingly real violence as it was in its folk-horror climax.

“It’d be a huge compliment if someone groups us with those guys,” Benson says. “But Ti West and Adam Wingard have watched a lot of films from the Eighties, including horror films, that come out as inspirations. Whereas Aaron and I don’t know the reference points at all.”

And he adds that one of the points of their work is to frighten audiences. “With our movies, we’re always trying to actually scare people, like Kill List and The Exorcist do,” he says. It’s just that it’s not as simple as “throwing violence at it, or jump scares, which are shallow for me. I believe that anyone can be terrified by one of our films, but you have to engage with it. You can’t have a few beers.”

Benson also finds the way horror is boxed in frustrating. “Once you get into ideas of genre,” he believes, “it becomes a bit absurd. It’s OK to categorise things – Wedding Crashers isn’t a horror movie – but we’re just trying to find a way to talk about how the world is. Man, if you think it’s horror, let’s talk about why you find it scary. That’s interesting.”

Moorhead and Benson are happy, too, to put love and relationships through the cosmic horror mincer. The Endless offers a world in which the deadbeat, virginal, bickering brothers played by its creators have to admit that a desert commune where looping eternity is only broken by temporary suicide, and an unseen cosmic entity is “using space and time as its horsewhip”, may in fact be preferable to their stunted normal lives.

The filmmaking duo also star in their latest movie (Arrow Films)

Their previous film, Spring, proffered a leisurely romance between a grieving young American man and an immortal Roman woman who sometimes grows fur, teeth, and tentacles like a queasy mermaid. Spring’s hero meets his monster lover in the aftermath of his mum’s death from cancer (rather poignantly, Benson has said all his films are inspired by his mum).

These days, Moorhead and Benson are now neighbours in the same LA apartment building, handily adjacent to an indie cinema; they work on their projects at Benson’s place.

But the work also springs from the pair’s opposite, complementary backgrounds. Young Benson was too busy attending San Diego punk gigs to be a film geek; Moorhead was meanwhile making amateur films in Florida, not watching them.

“I was raised atheist,” Benson says, “by a father who knows lots of science, and is highly sceptical. So when I tell a story, the otherworldly and supernatural appeals to me, because it provides the comfort of something more.”

“I was raised religious,” says Moorhead, “and it’s extraordinarily compelling and comforting to know that there’s more to all of this, and that something’s watching out for you. I wonder what it would be like to be a kid with just cold hard truth, unable to believe in magic or Harry Potter.”

Though they were ignorant of HP Lovecraft when they made their first two films, it feels like his concept of baleful old gods reaching into our universe crept in anyway. “When I’m writing a story,” Benson says, “I need to do it in a way that I can believe. I can’t tell a story about Satan, because I don’t believe Satan exists.

“But if someone said to me there is some sort of omniscient, all-powerful antagonist that predates human civilisation, but it’s influencing us and it’s around us and there’s a little bit of evidence, I couldn’t immediately go: ‘That’s made up.’ That’s one way our work is coincidentally Lovecraftian. It comes from how I was raised, and our storytelling instincts. We try very hard to create a myth no one’s heard before.”

The Endless is also about resisting the pressure to conform, whether in existing relationships between siblings, or bowing to apocalyptic extra-dimensional entities. What, then, are its makers rebelling against?

“When I was growing up I was much more of a conformist than I am now,” Moorhead says. “And as I’ve grown older, I very clearly see that no one has any idea what they’re doing. No one knows better than me. No one has any idea how our careers can and should go. So we made The Endless instead of a horror remake – and we’ve been offered all of those. That’s my form of rebellion.”

“We would like to make something a lot larger, because I want to pay our collaborators more,” he concedes. “And I want more people to see our movies.”

Their role models aren’t horror maestros, but the Coen brothers. “So people won’t go, ‘Oh, I don’t know how to market it, I guess we’ll just put a bloody girl on the cover.’ They’ll just put, ‘It’s a Moorhead & Benson movie’, and that’s why people will go see it. It’ll take 10 films in which we don’t screw up for that to even be a possibility. We want to hit a bullseye, on a really small target.”

While they aim for that, they can comfort themselves with The Endless’s success in the face of its awful circumstances.

‘The Endless’ is about resisting the pressure to conform (Arrow Films)

“Some nights would be really terrible,” Moorhead says of its shoot, “because his mum had just left us so recently. And it gets very quiet on that sort of day.”

But he also recalls a moment of strange benediction. They’d had a difficult period filming, hadn’t slept for two days, and were covered in dust and dirt as they drove out early one morning to get a final shot, listening to some “epic Lord of the Rings music” to keep powering them on.

“The sun was rising, and it was just so beautiful as it cracked over the desert mountains. We came round a curve, the music swelled, and there was this beautiful moment of victory, through the exhaustion and pain, that is frozen in my mind.”