Leonardo DiCaprio's new film is set to be huge. The true story behind it is chilling.

Killers of the Flower Moon is primed to sweep awards season.

It has all the ingredients of a critically acclaimed film. Two of the biggest actors of this generation paired with the most prolific director, recounting a story of one of the ugliest moments in America's history.

The Leonardo DiCaprio and Robert De Niro-starring and Martin Scorsese-directed film is based on real events: a series of murders committed in Oklahoma's Osage Nation during the 1920s.

The story of the tragic plight of the Osage went largely untold until journalist David Grann published his book Killers of the Flower Moon in 2017, which prompted further investigation into the region's dark history. 

"They suffered one of the most monstrous crimes in American history, yet many people, myself included, weren’t taught about it," Grann told The Telegraph. "We’ve effectively exorcised it from our consciousness."

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The film tells the story of the targeted Osage Nation murders of Mollie Kyle's (played Lilly Gladstone) family to gain access to their immense wealth. The murders were planned by wealthy rancher William Hale (De Niro), who married his nephew, Ernest Burkhart (DiCaprio), to Mollie.

Ahead of filming, Scorsese, DiCaprio and Gladstone visited the Osage to gain their consent to portray their story.

"They really worked hard at this and earned our respect," Chief Standing Bear said at the film's panel at Cannes Film Festival. "If you're not comfortable with Martin Scorsese, you're not going to be comfortable with anybody!" 

The director reportedly hired Osage people to work on-set, both in front of and behind the camera.

"You deal with Native Americans and Indigenous people, you gotta make sure everything we do, everything we do, is as authentic," Scorsese told CBS Sunday Morning. 

"We did our absolute best to listen to the Osage community," added DiCaprio. 

The Osage history that inspired Killers of the Flower Moon.

To understand what led to the murders in the 1920s, we need to go back another 50 years. 

In the 1860s, the Osage tribe (also known as 'People of the Middle Waters') were driven from their homelands in Kansas and negotiated a treaty to own what was presumed a worthless reservation in northern Oklahoma.

But while the rocky and barren lands were unfit for cultivation, they turned out to be extremely valuable in a different way: the land was rich in oil.

This part of Oklahoma became one the wealthiest areas in the world, and in turn, members of the tribe became the richest people per capita in the world.

The laws change after the Osage become rich.

At first, they were able to spend their riches, with some buying cars, luxury goods, building mansions, and hiring white servants. But in 1921, Congress established a a system appointing 'guardians' for the tribe – typically prominent white men who would manage the funds of Osage persons deemed "incompetent". 

Unsurprisingly, this system often led to guardians withholding and stealing money from the Osage people – in the film,  for example, Mollie has to visit her guardian to request access to pay medical bills with her family's own money.

Aside from becoming a guardian, another way to gain access to the Osage's riches was by marrying into the family. The mining money could be accessed through headrights, which meant that the land could only be inherited by an heir – and never bought – and only when the owner died.

This began the grim practice of white men marrying into Osage families and murdering their spouses to steal their family's wealth. "I don’t know of a single Osage family which didn’t lose at least one family member because of the headrights," Louis F. Burns, an Osage historian, said in the documentary Osage Tribal Murders.

Which brings us to William Hale – a wealthy livestock owner who married his nephew, Ernest Burkhart, to Osage woman Mollie Burkhart – and would become known as the 'King of the Osage Hills'.

Ernest and Mollie's controversial history.

Ernest met Mollie in Osage County when he was working as a taxi driver. By 1917, and under Hale's influence, Ernest married Mollie, and the couple had three children together: Elizabeth, James (aka Cowboy) and Anna.

The loving depiction of Earnest and Mollie's relationship in the film is something that's drawn criticism. Scorsese said that the portrayal came from a conversation with the couple's granddaughter, Margie Burkhart, who had an unexpected view on Earnest.

"She said we have to remember that Ernest loved Mollie, and Mollie loved Ernest," the director said during a press conference. "It's a love story. So what happened was the script shifted that way and it became gritty."

Image: Apple. 

Others have suggested that a man who spent his marriage plotting to murder his wife and her family should not be portrayed in such a sympathetic way. 

"When somebody conspires to murder your entire family, that's not love. That's beyond abuse," Osage language consultant Christopher Cote told The Hollywood Reporter at the premiere. 

The Reign of Terror begins. 

What happened next was known as this community's 'Reign of Terror'. 

Mollie's sister, Anna Brown, and cousin, Charles Whitehorn, were both found shot in the head in 1921 – and over the course of the next four years, Mollie's mother, two sisters and at least 21 members of the Osage Nation and their allies had all suffered violent deaths under suspicious circumstances.

At the same time, Ernest had been slowly poisoning Mollie by swapping her diabetic injections to keep her weak. However, despite Ernest and Hale's intentions, Mollie survived.

The federal goverment finally started investigating the series of murders in 1923, when Mollie's sister Rita's family and her housekeeper were killed in a bombing at their home. 

A team of government field agents led by former Texas Ranger Tom White (played by Jesse Plemons) was assembled, under an early iteration of the FBI known as the Bureau of Investigation, which was created by J. Edgar Hoover.

White and the investigative team found that Hale and a host of career criminals had orchestrated the Osage murders in an attempt to swindle their riches.

What happened next?

Hale and Ernest were arrested in January 1926 for the murders. Ernest eventually provided a full confession, naming Hale as the mastermind of the plan.

Ernest, Hale and accomplices John Ramsey and Kelsie Morrison were all sentenced to life in prison.

Image: Apple. 

The murders that Hale orchestrated were just one part of a much larger plan. It's been estimated that up to 60 people from the Osage community with headrights were killed between 1921 and 1926.

At the time, many in the Osage community were so frightened that they didn't leave their homes. "What I wanted to capture, ultimately, was the very nature of the virus or the cancer that creates this sense of a kind of easygoing genocide," Scorsese said during a press conference.

To prevent another Reign of Terror unfolding, Congress amended the 1906 act to forbid any non-Osage from inheriting headrights.

In 1947, after just 18 years in prison, Hale was released on parole – a decision that incited protests throughout the Native American community.

Ernest was released from prison on parole in 1937, which was the same year Mollie died at the age of 50. Mollie initially stood by her husband, but decided to divorce him after he confessed. She later remarried.

In 1966, Ernest received a full pardon from the Oklahoma Governor for his crimes. 

Feature image: Apple.