At a prim and proper girls’ school in 1960s England, things aren’t quite right. A strange illness is sweeping through the student body, causing dramatic fainting spells and undue stress to teachers who do their best to ignore the phenomena. Doctors can’t explain it. At the centre of it is the troubled Lydia Lamont, played with a mesmerising performance from Maisie Williams (Game of Thrones).

It’s hard not to think of Australian classic Picnic at Hanging Rock while watching The Falling. Both take a repressed, girls’ school setting and add an eerie layer of the unexplained to great, unsettling effect.

“You can’t be unhappy with that comparison, can you?” asks director Carol Morley.

In fact, it was in her mind when she was writing the script. Like in Picnic, the wild landscape is both beautiful and scary, totally at odds with the primness of the school, and the teachers seem to be fighting a losing battle against nature. “I kept writing in the script ‘nature presses in’,” says Morley. “We don’t have the dramatic nature of the Australian landscape, but I wanted nature to be a powerful force.”

The fainting spells are an example of “psychogenic” illness, Morley tells me, where emotions become so strong they manifest physically and become contagious. For Morley, it’s the perfect way to explore the tumult of growing up.

“These girls are invisible,” says Morley, “and the fainting spells are something extremely visible that can’t be ignored. It becomes a metaphor, to put it crudely, for what it feels like to go through adolescence.”

About the real-life condition Morley says, “Some people might think it’s the devil, some think it’s an illness, some think it’s just made up. We just don’t know.” Which is just as well, because the film isn’t interested in giving us answers. The Falling is about exploring the tight, repressed atmosphere of a school, a decade and a country, and seeing what happens when those tensions boil over. The ’60s, Morley believes, were an adolescent period. Man had made it to the moon, but women were trapped indoors. Meanwhile, the parade of male authority figures in the film simply can’t understand why the young women are behaving so oddly.

The dream-like atmosphere is underpinned by a haunting score from Tracey Thorn, (Everything But the Girl). And like something in the film, Thorn’s involvement came from a dream.

“I had a dream that Tracey Thorn had already written the music. I didn’t know her, but I contacted her on Twitter and gave her the instruments from the school orchestra scenes in the film, and that’s how she composed.

“I told her I didn’t want a soundtrack that signalled the ’60s, I wanted a score that manifests what it feels like to be that young.”

On a basic level, that’s what the film is about.

“It’s about that complicated dichotomy of teenage life,” says Morley. “On one hand you don’t want to be noticed, but on the other hand you’re desperate to make a mark.”

The Falling is showing now at ACMI until July 26. Another of Morley’s films, Dreams of a Life, is also screening.