Martin Scorsese and Leonardo DiCaprio have officially settled on their next collaboration.

The iconic director and Oscar-winning actor are officially attached to the adaptation of David Grann's book "Killers of the Flower Moon," according to Deadline. Eric Roth ("Forrest Gump," "The Curious Case of Benjamin Button") will write the script.

Based on a true story, the thriller is set in 1920s Oklahoma when the Osage Nation were the richest people per capita in the world, after oil was discovered under their land. Then, they were murdered one by one. The newly created FBI began to investigate and unraveled a chilling conspiracy — one of the most heinous crimes in American history.

“When I read David Grann’s book, I immediately started seeing it—the people, the settings, the action—and I knew that I had to make it into a movie,” said Scorsese. “I’m so excited to be working with Eric Roth and reuniting with Leo DiCaprio to bring this truly unsettling American story to the screen.”

Filming is likely to begin next summer. Scorsese is currently in post-production on his Netflix gangster movie "The Irishman." DiCaprio is currently shooting Quentin Tarantino’s "Once Upon a Time in Hollywood." They last collaborated on 2013's "The Wolf of Wall Street."