In his follow up to the award-winning Dallas Buyer’s Club, Canadian Jean-Marc Vallée tells of another true story with the visceral, introspective, and poignant Wild. Based on the memoir by Cheryl Strayed, it follows Reese Witherspoon as Strayed, a woman singularly venturing on a months-long hike as she confronts a past that involves a divorce, drug abuse, deviant sex, and a complex relationship with a mother who has passed away.

“I read the first draft, and then I read the book, and it was so powerful, so rich, and so emotional,” said Vallée in measured speech during a roundtable interview in Toronto. To encapsulate such a story, Vallée opted to focus on the mother-daughter relationship as much as he could, with actress Laura Dern as Strayed’s mother, appearing in flashbacks and visions throughout the film at various stages of her life.

“Even then when I was waiting, for Reese or something else, I was shooting some footage with Laura to get more presence of the mother,” Vallée continued. “The first time I saw her, I was in the trailer shooting Reese alone doing the makeup, and said let’s shoot you on the trail, maybe we’ll use you.”

“Everything single shot we ad-libbed with Laura, maybe 10 to 12 of them, are in the film. It was nice to be emotionally creative on the spot.”

It’s a delicate balance between being faithful to the source material and the true story while also running off to improvise scenes, but for Dern and Vallée it wasn’t complicated. She immersed herself in the character while Vallée held together a vision of the final film in his head.

“It’s one thing as an actor to get the opportunity to do that and try to find things and invent things, a it’s another thing for a filmmaker to say Reese isn’t ready, let’s go shoot with Laura; he s always coming up with something,” said Dern who also came to Toronto for the film’s premiere at TIFF. “It’s another thing to have a great editor and director. The way he weaves memory in non-linear way – people like stories to unfold with a beginning, middle, and end, but that’s not the way memory comes to us. He plays with that so beautifully.”

Strayed was present on set to help Witherspoon and Dern better relate to the story, and Dern especially felt a responsibility and care to portray her mother.

“If I didn’t spend as much time with Cheryl as I did and didn’t hound over the book, it would not have been fair to do what we did,” she explained about the improvisation. “We did it from her memory, the feelings she was sharing. We capture the fun and cuddles and intimate moments. A lot of our improv was to get to a line Cheryl said, even in the book and not in the book; lines not in the script that I remember or Cheryl shared and then I was able to kind of bring it back.

Beyond simply recreating Cheryl’s mother, Dern found herself in a unique position. Cheryl’s young daughter is in the film, portraying her own mother at a young age. Cheryl’s daughter never had the chance to meet her grandmother, but with Dern assuming the role, there was able to be a vision of this woman and a mother-daughter relationship that her own daughter could witness, if only for a fleeting amount of time.

“The responsibly to honor someone and never betray their story, you get very protective of it,” explained Dern. “It was a great privilege, and Cheryl speaks about it beautifully in that her great heartbreak was that her children never got to meet her mother.” Cheryl told Dern of her daughter, ‘she is knowing her grandmother through you.’

“She did really get to know her grandmothers and mother’s relationship,” continued Dern. “To sit there with Cheryl’s daughter, it was an amazing experience.”