In 2017, author David Grann wrote Killers of the Flower Moon, a riveting and jaw-dropping tale about the mysterious and extremely callous murder of the Osage tribe. The book is being turned into a movie this October, so here’s what you need to know before watching.

Between 1920 and 1925, over 60 confirmed murders took place in Osage county, all related to Osage headright holders, all extremely mysterious. Most of these cases remained unprosecuted or even investigated. In the book, Grann opens up the wider conspiracy behind these killings that may have numbered in the hundreds.

In the early 1920’s, the Osage tribe became the richest people in America per capita through the oil industry, earning more than $30 million in 1923 alone. The booming oil industry attracted tens of thousands of workers along with many white opportunists to Osage county, completely pivoting the economy of the region.

During the industry’s economic upturn, the American system failed the Osage people miserably. Racism of the American economy drove the financial structure of Native American life. Although they owned the land and gained the royalties, the U.S. government tightly regulated the way in which the Osage people lived. White settlers prided themselves on the way in which the law protected individuals’ rights. But with the Osage tribe, the law neglected them.

The investigation into Osage tribe rights was a large contributor in the formation of the FBI. It was their first case into not only systemic embezzlement, but also large-scale homicide. Bureau director J. Edgar Hoover had started investigations into the case but it backfired quickly, after which he was forced to turn to private investigator Tom White, who was able to crack the majority of the solved murders. White is the individual credited in the book as well as the movie for his dedication to the case.

The film comes out on Oct. 20 on Apple TV. It is directed by Martin Scorsese and stars Leonardo DiCaprio, Robert De Niro and Lily Gladstone. 

Peter Bradshaw of The Guardian described the film as “…an utterly absorbing film, a story that Scorsese sees as a secret history of American power, a hidden violence epidemic polluting the water table of humanity.” 

It’s astonishing how long the American public went without knowing or even investigating the story of the Osage tribe. An extremely historic and significant piece of Native American history once again completely buried. 

Being nearly three and a half hours, the movie carefully follows the investigation into the Osage murders. The cinematography is beautiful and perfectly captures the material wealth that the Osage tribe had at the time. It has been reviewed by critics as “stunning” and a “staggering piece of cinema and an urgent social probe and trial” by Rotten Tomatoes.

Make sure to watch Killers of the Flower Moon on Apple TV starting Oct. 20.