Leonardo DiCaprio and Lily Gladstone Star in Epic New Trailer for 'Killers of the Flower Moon'

Leonardo DiCaprio and Lily Gladstone play an unlikely pair caught between greed in 1920s Oklahoma.

In the new full trailer for director Martin Scorsese's Killers of the Flower Moon, the pair star as Ernest Burkhart and Mollie Kyle, who strike up an "improbable romance," per a synopsis.

Based on David Grann's 2017 bestseller about a true story, the film "is an epic western crime saga, where real love crosses paths with unspeakable betrayal."

"Oil brought a fortune to the Osage Nation, who became some of the richest people in the world overnight," the synopsis adds. "The wealth of these Native Americans immediately attracted White interlopers, who manipulated, extorted and stole as much Osage money as they could before resorting to murder."

The cast also includes: Robert De Niro, Jesse Plemons, Tantoo Cardinal, John Lithgow, Brendan Fraser, Cara Jade Myers, JaNae Collins, Jillian Dion, William Belleau, Louis Cancelmi, Tatanka Means, Michael Abbott Jr., Pat Healy, Scott Shepard, Jason Isbell and Sturgill Simpson.

Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.

In May, DiCaprio, 48, told Deadline about the complexities of the film's story.

"Ernest and Mollie really represented how twisted and complex some of this stuff was, culturally,” he said. "A lot of Osage women were marrying White men who really came to prey on them, to take over their headrights and seize their oil money."

"And yet, at the same time, what struck me was one scene in the initial draft we had, the real testimony of Ernest and Mollie, as he explains his part in this horrific plan," he added. "They still loved each other. That was the twisted complexity of what made this a truly dark American story.” 

This is DiCaprio's sixth film with 80-year-old Scorsese. They previously worked together on Gangs of New York (2002), The Aviator (2004), The Departed (2006), Shutter Island (2010) and The Wolf of Wall Street (2013).

DiCaprio told Deadline they "did a lot of work to try to help Marty do what he does best, which is to tell a very human story."

“To get to the dark side of the human condition but also understand the complexities," said the Oscar winner. "Here you had the wealthiest nation, the richest per capita people in the world. You had this melting pot in Oklahoma where freed slaves had created their own economy, and the Osage emerged as this wealthy culture."

"But," he continues, "you also had during that period the rise of the KKK and white supremacy and this clash of cultures. For some of these White settlers, it was like a gold rush to take advantage of people of color."

Killers of the Flower Moon is in select theaters Oct. 6, then everywhere Oct. 20, before later streaming on Apple TV+.