Thinking about casting the world’s biggest pop star in your microbudget indie? Four days before shooting Erupcja in Warsaw, Pete Ohs discovered that Charli xcx would have to leave early for a Converse commercial in London. As Erucpja, a film that could alternatively be called volcano, so confusing, was meant to be shot chronologically, the story was radically reworked on the spot. Still, the singer’s presence means Erucpja will have more viewers than Ohs’s previous five films combined.

However, Ohs, who’s shot five films in five years, thrives on spontaneity. As per his process, the director writes the scenes with his actors the night before, or on the morning, they’re shot. Before principal photography, only the story’s first half is sketched out; the second half is then constructed once the first half is filmed. It’s why Erupcja credits its screenplay to Ohs and its four main actors: Charli xcx, Lena Góra, Will Madden, and Jeremy O. Harris.

In May 2024, a month before Brat came out, Ohs was introduced to Charli xcx by their mutual friend, Jeremy O. Harris, at a New York bar. Learning about Ohs’s improvisational methods, the singer agreed to shoot Erupcja three months later in Poland despite – or because of – the absence of a script. All she knew was that the storyline would thematically involve female friendship and volcanoes. “Charli had a lot going on with brat summer,” Ohs tells me over Zoom from New York. “It felt bad to be losing our actress early to a Converse ad. But it was also an opportunity to do something different with the narrative.”

Whether it’s because I’ve thrown the question at him, or if he’s being genuine, Ohs explains how brat summer infiltrated Erupcja. “The brat phenomenon was also a volcanic eruption,” says the softly spoken, 43-year-old American director. “Maybe subconsciously, we made a film that’s also part of that conversation. Is being brat cool? Does being brat hurt other people? Should brats apologise sometimes? Maybe!” He laughs at his answer. “What excites me is that it wasn’t calculated. It’s just artists being present, responding to the moment” – he gives a knowing look after the accidental wordplay – “and making something relevant to what’s going on.”

Like The Moment, a mockumentary about Charli xcx escaping to a European city amidst brat summer, Erupcja stars the singer as a grounded alternative to her pop star persona. In Warsaw, Bethany (Charli xcx) has arrived with her boyfriend, Rob (Madden, a doppelganger for Charli’s IRL husband George Daniel), for a romantic getaway. Whereas Rob secretly wishes to propose during the vacation, Bethany prefers to party with an old friend, Nel (Góra), a local with her own relationship strife. The low-key hangout-drama then reveals that Bethany and Nel carry a superstition: whenever they meet, a nearby volcano tends to erupt.

Indeed, Bethany possesses more chemistry with Nel than Rob, and Erupcja proceeds to showcase Bethany and Nel as the story’s most magnetic duo. Elsewhere, a highlight is Agata Trzebuchowska as Nel’s girlfriend, Ula, marking her first significant acting role since Ida. Ultimately, though, Ohs knows what viewers want to watch: the film is essentially Charli xcx having an existential breakdown in the streets of Warsaw. (A tearful monologue from Bethany proves that the singer can actually act.)

“I was aware of the song [‘girl, so confusing’] and the Lorde remix,” says Ohs. “Charli was in the middle of finishing the masters of the remix album during the shoot. Lena and Charli were hanging out and discovering their characters. They shared anecdotes, ideas, and how it reminded them of past relationships they’d had. How I make movies is that, if it was a different set of people, it would be a different movie. Because it’s Charli and Lena, they’re bringing what they’re bringing, and we end up making a movie about fraught female relationships. What the process asks is for everybody to be pretty vulnerable, and to bring themselves to the project.”

The film’s freewheeling charm is reflected by its production. Doubling as the cinematographer, Ohs writes the screenplay on his iPhone’s Notes app and sends scenes to the cast through a group chat. Scenes tend to be written when the cast sit down for meals – when Bethany and Rob have leftovers at a pizza restaurant, it’s simply what Charli xcx and Madden were eating before the cameras were rolling.

“I make movies by removing pressure,” says Ohs. “Writing on the Notes app means never having to face a big, blank, white page. It updates collaboratively. If the actors want to make changes, they can.” Do ideas come differently if you bash out an entire screenplay on your phone? “I like to work intuitively. Maybe that’s a problem: we’re all trained to feel good picking up our phone and typing. But it feels so natural. The smallness allows me to zone in on the scene I’m trying to write.”

“To make a movie where you’re jumping off a cliff into the unknown, and you don’t know where the story is going to go – that’s similar to how life is lived”

While Ohs’s method sounds like he’d produce the kind of unscripted dramedies churned out by the Duplass brothers and Greta Gerwig in the mumblecore movement, his influences are more akin to European arthouse cinema: he namechecks Pasolini, Antonioni, and Italian neorealism. In the style of early Godard, Erupcja has a dryly witty, third-person narrator. “I love the spirit of the mumblecore movement, which is friends making things together,” says Ohs. “But my films are more aesthetically drawn to the French New Wave.”

Ohs has tried the traditional method of writing a script, finding financing, and then shooting it, with 2017’s Everything Beautiful Is Far Away. Made for $200,000, it failed to raise much attention; Ohs has previously questioned whether it was worth seven years’ worth of investment. He’s now set upon the method that produced Erupcja: crucially, it always starts with a geographical location, not a person or plot. In the next year, he plans to shoot two movies (“two different places, ready to go”) with the same improvised techniques, albeit on a larger scale. “The challenge is to engage with a bigger framework,” he says. “Does the method hold or crumble?”

The obvious comparison is with early Wim Wenders. In his golden streak of films like Paris, Texas and Alice in the Cities, Wenders would also pick locations and discover the film as he went along. “The way you make a movie will directly inform how that movie feels,” says Ohs. “Marvel movies feel the way they do because of the process they use. To make a movie where you’re jumping off a cliff into the unknown, and you don’t know where the story is going to go – that’s similar to how life is lived. That’s why Wim Wenders’s films feel the way they do. Not every movie can, or should, be made that way. But it results in a really specific, special feeling.”

Erupcja is out in UK cinemas on June 5.