Film-maker Adrian Chiarella knows there’s nothing more terrifying than what you’ll read in the news. As a gay man, he has long been horrified by reports of religious leaders everywhere from the US to Indonesia attempting to purge “homosexual demons” from young people as they cry, convulse and vomit. The horror buff in him could see a great scary movie in these modern-day exorcisms – but there was just one problem.

“The more I explored that directly as an idea for a horror movie – like, what if it was literally about an exorcist that comes and performs this ritual? – the more it seemed to justify the belief those people had about a ‘gay demon’,” Chiarella says. So instead, he started asking, “Well, what’s the opposite of that?”

Chiarella’s search to subvert the idea of an exorcism became the premise of Leviticus, which premiered at the Sundance film festival in January and screened at the Sydney film festival this month. Instead, his version of an exorcist ritual doesn’t banish a demon but ushers one in.

The film centres on two teenage boys, Naim (Joe Bird) and Ryan (Stacy Clausen), who embark on a tentative romance in their Bible belt Australian town. But once their parents get a whiff of what’s going on, they are hauled to church and subject to a religious ceremony – which unleashes a shapeshifting bogeyman that takes the form of whoever its victim is most attracted to. Suddenly, Naim and Ryan must wonder if that teenage boy standing in the shadows is really the guy they’ve been stealing kisses with, or a monster hellbent on leaving them dead.

It’s a creepy horror flick with lots to say about the shape of modern homophobia – and looks poised to be a hit. During Sundance, Leviticus was bought for A$7.1m by distributor Neon, which is giving the film a US release the day after it hits Australian screens on 18 June. Early reviews have been positive, while audiences at the Sydney film festival rushed to Letterboxd to interpret the film’s socially pointed Big Bad – a monster Chiarella wanted to keep “broad enough” to relate to anyone’s experience, despite coming hot off the heels of the conversation around the recent New South Wales conversion practices ban.

“People say to me, oh, it’s a conversion therapy metaphor, and I’m like, not necessarily,” Chiarella says. “It can stand for anything in that space around the coercive measures different communities come up with to control young people’s lives when they’re going through this stage of their development.”

The dread and terror in the film comes not just from that ever-stalking entity but the ordinary humans around Naim and Ryan. There are the townspeople who seem unwilling to step up and protect their young men; a culpable inaction that could stand in for everything from the early days of the HIV epidemic to the politicians who allowed hateful rhetoric to spread during Australia’s marriage equality debate. And, of course, there are the God-fearing parents who volunteer their sons for exorcism and welcome the demon into their lives under the pretence of “helping” dissuade them from their desires.

Chiarella originally conceived of Naim’s religious mother, Arlene (Mia Wasikowska), as a classic, malevolent “horror mum”, à la Piper Laurie in Carrie. He later realised “there’s something more terrifying about her just being so underhandedly natural and, in this very straightforward way, just going, ‘This is what I believe’”.

He also knew that for the horror of what can be done to young people in the name of faith to really resonate, Leviticus needed actual teenagers in the two lead roles – a casting “challenge” for any film-maker, and the reason so many teen films are populated by actors on the other side of 25. Eventually Chiarella found the then 18-year-old Bird, an Adelaide native who viewers may recognise from his pivotal role in another Australian horror movie, Talk to Me: the 2022 box office smash that grossed A$140m worldwide.

Leviticus owes a certain stylistic debt to that Philippou brothers film: both take place not by the beach or the bush, but in a bleaker, greyer middle Australia (Talk to Me in the suburbs of Adelaide; Leviticus was shot on the dreary outskirts of Melbourne). The broad Aussie accents, funnel web spider references and shots of ageing weatherboard houses add to that sense of place, while the natural landscape brings its own hostility – Leviticus’s monster can only appear when its victims are alone, making the underpopulated, wide open spaces of regional Australia a scary place to be.

Chiarella wanted both international and local audiences to recognise his film as Australian. After the recent global success of Talk to Me, plus enduring legacy horror films like The Babadook and Lake Mungo, it felt like something genre fans were eager for more of.

“I was very aware that we were going to make a film that fit into this ‘Aussie horror’ sub-genre … We didn’t want to hide that fact, we really wanted to embrace it.”

For his part, Bird says that while he “loves horror so much”, he did not set out to become a homegrown scream king.

“It’s not necessarily that horror is this genre I’m chasing after – I think that Australia has just been creating great scripts that happen to be in the horror space.”

But what both Bird and Chiarella think is unique about Leviticus is the queer love story hidden between the jump scares. After all, what could be more romantic than telling your crush that if you have to be stalked by an unstoppable murderous entity, you’re glad it looks like them?

Chiarella thinks most horror movies have “a much more cynical point of view” than Leviticus. “Ours, I think, is a much more sincere love story about growing up and what it means to be a teenager,” he says. “We’ve got some scares, we’ve got some nods to the gory history of horror, but ultimately it’s a movie about finding first love.”

• Leviticus is released on 18 June in Australian cinemas and on 19 June in the US