When Michael Pitt first heard the elaborate science-fiction tale that would become “I Origins,” he was so captivated he believed it was a true story.

Pitt had requested a meeting with Mike Cahill, the young director who wowed Sundance audiences with his moody debut feature “Another Earth.” As Cahill discussed his concept for “I Origins,” which raises questions about the afterlife through a fictional scientific discovery about the human eye, Pitt was convinced.

“It was just such an interesting concept,” Pitt said. “After he finished, I wasn’t surprised. I was like, ‘Where can I read about this?’ Because I thought it was true. He was like, ‘No, I just made it up.’”

During a recent interview in Toronto, Cahill and Pitt laughed as they recalled their first meeting. But Pitt, best known for his role as Jimmy Darmody on HBO’s “Boardwalk Empire,” remembered telling Cahill that viewers would be equally spellbound by his fascinating idea.

“If you can make a film where you’re doing that to the audience, I would just die to see that,” he told the director.

The comment “set a wildfire” in Cahill’s mind, he said, and he wrote a rough draft of the script in a few weeks. “I Origins” won the Alfred P. Sloane prize at Sundance earlier this year and opens Friday in Toronto and Vancouver before being released in other Canadian cities.

Pitt plays PhD student Ian Gray, who falls in love with an enigmatic beauty named Sofi (Astrid Berges-Frisbey) after photographing her unusual and striking eyes. When their relationship is suddenly cut short, Gray delves deeper into his studies on the molecular biology of the eye with his lab partner Karen (Brit Marling).

The pair stumble upon startling evidence that leads Ian to question his once-certain scientific views. As he embarks on a journey to India to confront his past with Sofi and her unique irises, he is forced to confront the possibility that there is more to life than science can explain.

Cahill also explored vast existential questions in “Another Earth,” which starred Marling, his collaborator and friend. Through the looming image of a duplicate Earth in the night sky, the film considered what a new world could mean for two people with tragic pasts.

In “I Origins,” Cahill wanted to explore the question of science vs. faith because it’s fundamental to human existence, he said.

“It’s undeniably something you have to look at if you’re not numb in life. If you actually want to confront what being a human is, you have to confront that question of: ‘What are we? Are we molecules and atoms, or is there some entity that persists after all that stuff?’

“We don’t have to have the answer but we can provide a narrative that seems to make sense and may give us hope. I love that and hope to continue to have opportunities to do that,” he said.

Pitt did significant research for his role as a molecular biologist, even visiting Johns Hopkins University and shadowing a DNA researcher. He said the film transcends the stereotypical stuffy image of scientists.

“There’s this stigma about scientists, that they’re really dry and have a lack of emotion. The truth is that they’re some of the most passionate people in the world,” said Pitt. “I think it’s important to show them like that.”

The experience of making the film also gave him a deeper understanding of science and faith, he said.

“It certainly informed me a little more. I was given the opportunity to really designate some time to researching these interesting things,” he said. “The best movies that you work on definitely change you and inform you too. This was certainly one of them.”