Andrew Nadkarni wanted to tell his tree-climbing aunt’s heroic story. Then he learned about their family’s trauma.

Filmmaker Andrew Nadkarni’s earliest memory of his aunt is of her visit to his elementary school, the School in Rose Valley. It was no regular career presentation: Nalini Nadkarni arrived with mountain climbing gear and took the kids outside. The ecologist used her own slingshot-like invention to rig a rope on a 15-foot-tall tree branch and climbed up the trunk. It was a small-scale demonstration of the 200-foot vertical journeys she braves to study canopy ecosystems all over the world.

“I was always looking up at her. Here’s this superhero. Magnetic, shiny, not afraid, you know, this perfect explorer and adventurer,” Andrew, who grew up in Media, told The Inquirer.

As a middle schooler, he raved about Nalini appearing in Playboy — she was named on a list of the most interesting college professors — and as student council president of his high school, Wynnewood’s Friends’ Central, he invited her to speak to his peers.

Nalini Nadkarni went on to create a TreeTop Barbie to encourage young brown girls to pursue science, win awards for her pioneering research, land a biology professor job at the University of Utah, and earn the moniker “Queen of the Forest Canopy.”

But it wasn’t until much later that Andrew learned what pushed Nalini to begin escaping into treetops in the first place.

In 2020, Andrew was filming Nalini for a short documentary about her exploration, focusing on her recovery from a nearly fatal fall in 2015 that broke her back and ribs. In their interviews, Nalini opened up to her nephew about healing physically, and how that process made her face older, deeper wounds.

“I remember when I was 8 or 9 years old, taking this very solemn oath,” Nalini says to Andrew in his 2023 film, Between Earth & Sky, screening at the Philadelphia Film Festival this week. “When I grow up, I want to do something that protects trees. Something that pays them back for the sanctuary that they gave to me as a kid.”

Nalini grew up in Bethesda, Md. a leafy suburb of Washington, D.C. as one of five kids. She was sexually abused by her father and forced to keep it a secret from her siblings and mom. That violence led her to spend hours outdoors, looking for comfort in nature. She found it in her neighborhood’s maple trees.

“The trees were there as my witness,” Nalini tells her nephew in the film. “They were dependable. You could trust them.”

This was a horrific truth that Andrew didn’t expect to excavate while filming. He was a baby when his grandfather died. “I didn’t know my grandfather, but I thought of him as this noble, sort of upstanding citizen, a moral authority,” he said. That image shattered, he wanted to investigate further. With Nalini’s permission, he began talking to his father — a doctor at CHOP — and other relatives.

“I was like, ‘What is going on here? Am I being the therapist for my family?’ ” said Andrew. “I was trying to echolocate my own understanding of who I am and where I came from.”

That footage isn’t part of Between Earth & Sky, Andrew’s directorial debut. The film centers Nalini’s enormous resilience and infectious Ms. Frizzle energy around scientific discoveries.

Andrew is heartened that the family has supported him, Nalini, and his film.

“Everyone was ready and understanding of how brave it was for Nalini to share this,” he said. He recalls holding hands with Nalini as they attended the first screening together. “Despite all of the risks … the family has embraced the film and is happy that it’s out there, even though there are difficult truths that are shared.”

Nalini was hesitant when the documentary began showing at film festivals. It took a few times before she could see that she would not be a subject of shame or judgment for sharing her story. Her openness connected with viewers. Last week, the National Geographic Society named Nalini an “Explorer at Large,” the highest distinction within the organization.

In the film, Nalini climbs her favorite tree, an over-200-feet-tall strangler fig in Monteverde, Costa Rica, named Figuerola. Despite the fall a few years ago, she expresses feeling cozy, at home among the canopy. That day, Andrew joined her to capture the lush, rare view so high up. There was a slight hiccup: He stopped at the wrong branch, lower than where they planned. The result was a low angle with the camera viewing Nalini through the leaves.

It’s Andrew’s favorite scene. He’s always looking up at her.

“Between Earth & Sky” screens at Philadelphia Film Festival as part of its live action shorts program. It will be shown on Wednesday Oct. 25 at 3:45 p.m. and on Saturday Oct. 28 at noon. On Saturday, director and producer Andrew Nadkarni will participate in a Q&A session. The documentary is also available to watch on PBS. It’ll also play at the Philadelphia Asian American Film Festival next month.