In this new crime thriller, the Obi-Wan Kenobi star portrays a reformed neo-Nazi, Narvel Roth, who works as the head horticulturalist at a large estate. Here, he eventually strikes up a relationship with his apprentice Maya, played by Quintessa Swindell (an actress 23 years Edgerton's junior).
According to Edgerton, he immediately "grilled" Schrader about this upon reading the script.
"I said, 'Do you see this relationship as something you want the audience to be thrilled by in a way that's titillating or pleasurable?' And he said, 'No, I want people to be confronted by it,'" the actor told NME.
His initial reservations stemmed from an experience he once had with a different movie.
Apparently, Edgerton managed to miss the beginning, walking in just as an unnamed older actor was chatting to a younger woman in a bar scene.
"I'm trying to work out what I've missed in the film," he recalled. "And then he leans in to kiss her, and I'm like, 'No!' It was the age difference!
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"I had assumed it was a father-daughter relationship. But this actor had cast a girl as his love interest, and I was straightaway really angry about it. So I was very cautious about this relationship in [Master Gardener]."
Watch: The Underground Railroad: Director Barry Jenkins and stars Thuso Mbedu and Joel Edgerton speak to Sky News' Backstage podcast