Actors Robert DeNiro, Leonardo DiCaprio and director Martin Scorsese at the premiere of the film "Killers of the Flower Moon" at Cannes, France, May 2023 (AP)

Writer David Grann, of the book that legendary director Martin Scorsese has made into the film called "Killers of the Flower Moon", says that the trick to consecutive successions is making incredible facts seem "plausible".

Starring Leonardo DiCaprio and Robert DeNiro, the film speaks volumes of a true-life incident of murder and exploitation among the Osage Native American community in 1920s America. The film comes to cinemas and Apple TV in October, having already premiered at the Cannes Film Festival earlier this year.

Grann, who wrote the book under the title "Killers of the Flower Moon: The Osage Murders and the Birth of the FBI", expressed that he is a fan of Scorsese's adaptation.

During his visit to Paris, he told AFP: "The Osage were deeply involved in the production. That's what makes the movie so powerful. It's shot on location, in the very places where this occurred".

Even before it was done, Apple already bought the rights to "The Wager", Grann's next work, for Scorsese and DiCaprio to adapt. "The Wager" is about the story of the British ship, HMS Wager, that was wrecked off the coast of South America in 1741.

These are not Grann's first adaptations, as his previous works include "The Lost City of Z" and the story of "The Old Man and the Gun" starring actor and Sundance Film Festival founder Robert Redford.

Not all film is make-believe

Grann, in his writing, usually leaves himself or his experiences out of the content. For example, in his latest book "The Wager", he left out the fact that he visited Wager Island in Chile, where he saw the remains of the HMS ship.

"I don't write about my own trip because I felt it would have been an intrusion. And yet, that trip was so essential in all my descriptions, and to bring life to them," he said, as the castaways spent five months of winter on the wind-blasted, starving and cold.

Because it was almost too hard to believe that they could have barely survived the barren place, the writer felt no need to exaggerate or go overboard, and rather said that the hardest task was making the truth "look plausible".

"There is a lot of tedium about doing the research. But the fun is when you come across things that make your jaw drop," said Grann, who is also a staff writer for The New Yorker.

One of the moments that made his jaw drop was when he stumbled upon the original journals, which in some way survived, that showed that the ship lost all its sails in a hurricane.

Outbreaks of typhus and scurvy were a problem at the time but the only possible solution was to make the crew climb the masts, hold onto the ropes and use their bodies as sails.

"I mean, you couldn't make that up, right?" he said, adding: "If they find the right story, people like to take liberties. I'm like, no! Why would I take liberties? So many things are happening".

However, he explained that there still was the need to separate fact from fiction.

"In exploring the facts, you have to explore how they give way to the legend".