For “Sacred Creatures” director Frieda Luk, belief can be comforting, ridiculous, exhilarating and hard to explain.

“I’m really fascinated by when people believe in something,” she tells Variety. “One person believes in something, and then a group of people, and then it slowly becomes this massive phenomenon. It goes viral.”

That fascination drives Luk’s debut feature, which world premieres in competition at the Edinburgh International Film Festival. Starring Olivia Luccardi, James Cusati-Moyer and Romina D’Ugo, the Canada-Italy production follows three estranged siblings reuniting in rural Italy after middle sister Miriam (Olivia Luccardi) is released from psychiatric treatment following an experience she understands as a spiritual awakening rather than a breakdown.

“This movie is my exploration of believing in something and belief,” says Luk. “Miriam has agency. She knows herself and she makes choices. However, when she becomes a figure that people rally around, people are imbuing her with meaning. When she becomes abstract, she no longer controls the message.”

That uncertainty extends to the film itself, which slips between psychological drama, comedy and magical realism without settling comfortably into any of them. For Luk, the tonal slipperiness developed naturally from writing. “I set up the situation and these characters, and as I’m writing, I’m following what they’re doing. What I’m waiting for is how they surprise me,” she says.