Killers of the Flower Moon, the film based on David Grann’s novel of the same name, marks one of Martin Scorsese‘s latest projects. It also serves as a major turning point for the critically-acclaimed filmmaker, who reportedly made extensive rewrites on the film.

The upcoming western drama follows the tragic murders of members of the Osage Nation in Oklahoma in the early 1920s.

While Grann’s book hones in on the establishment of the FBI and agent Tom White (originally Leonardo DiCaprio but now played by Jesse Plemons), Scorsese and DiCaprio realized that the film needed to focus on the relationship between Osage member Mollie Kyle (Lily Gladstone) and WWI veteran Ernest Burkhart (DiCaprio) instead.

“After a certain point, I realized I was making a movie about all the white guys,” Scorsese admitted to TIME magazine, “meaning I was taking the approach from the outside in, which concerned me.”

His final result, which he described as “a sober look at who we are as a culture,” is what Gladstone, whose father is Blackfeet and Nez Perce and whose mother is white, described to Vulture as “not a white savior story.”

“It’s the Osage saying, ‘Do something,'” she added. “Here’s money. Come help us.”

She commended Scorsese for highlighting Indigenous voices such as her own, saying that he “expected [her] to bring a lot to the table.”

Scorsese told TIME that he was attracted to the film and Grann’s book by its stark juxtaposition between “flowers” and “killer moon” in the title.

“It was an impression, like a haiku, almost,” he said.

He also elaborated on the current “cinematic culture,” which he believes should be unified, but right now “is being fragmented and broken up in a way.” He cited genres as being divisive among moviegoers, despite the fact that genres have always existed.

“Not everybody liked musicals. Not everybody liked westerns. Not everybody liked gangster films or noirs. But at the time, we just went to the movies, and that’s what was playing,” he explained.

Killers of the Flower Moon makes its theatrical debut on Oct. 20, followed by an Apple TV+ streaming release.