Early in Martin Scorsese’s “Killers of the Flower Moon,” an Osage woman named Mollie gives her gravely unsuitable white suitor, Ernest, a Stetson. It’s a large off-white hat with a bound-edge brim and a wide ribbon around the band. It’s a gift but it feels more like a benediction, and anyone who’s ever watched an old western film (or “Star Wars”) will recognize the symbolism of her largess. Mollie is telling Ernest that she sees him as a good guy, even if the movie has already violently upended the familiar dualism of the white hat vs. black.That dichotomy shapes “Killers of the Flower Moon,” a deeply American story of greed, betrayal and murder told through the anguished relationship between Mollie (Lily Gladstone) and Ernest (Leonardo DiCaprio). It’s around 1919 and Ernest is wearing his World War I uniform when he dismounts a train in Fairfax, an Oklahoma boomtown where luxury cars rumble down dirt roads. He’s come to live with his uncle, William Hale (Robert De Niro), a smooth-talking rancher who, in one breath, asks him if he has seen bloodshed and, in the next, describes the Osage as the finest and “and most beautiful people on God’s earth.”The movie is based on David Grann’s appalling, all-too-true crime book from 2017, “Killers of the Flower Moon: The Osage Murders and the Birth of the F.B.I.” In adapting it to the screen, Scorsese and Eric Roth have dramatically narrowed the role of the F.B.I. to focus on the multiple murders — scores, perhaps hundreds — of Osage members that took place largely in the 1920s on the tribe’s oil-rich reservation in northern Oklahoma. As the 19th century gave way to the 20th, oil made the tribe among the wealthiest people in the world. It also made them the target of numerous white predators. As a 1920 article in Harper’s ominously put it: “The Osage Indians are becoming so rich that something will have to be done about it.”The following year, Congress passed a law that required the Osage to prove they could handle their reserves “responsibly.” If they couldn’t, they were declared incompetent and appointed a guardian; it was a status, as Grann explains, that was usually given to full-blooded Osage like Mollie. It’s instructive then that the first time you see Mollie in “Killers,” she is in an office being asked to state her name by an unseen man. “I’m Mollie Kyle, incompetent,” she says, her face a serene blank. The man is her guardian, yet another smooth talker, though one with a picture of a Ku Klux Klan rider on his wall. When Mollie leaves his office, Scorsese cuts to a shot of her feet on a doormat imprinted with “KIGY,” an abbreviation for “Klansman, I greet you.”Mollie gives Ernest the Stetson soon afterward in a sequence that both lays out many of the story’s themes and beautifully illustrates dialectical filmmaking in four or so revelatory minutes. It opens at the 22-minute mark with Mollie walking away from the camera while coyly looking over her shoulder at Ernest, who’s watching her from a car. By that point, he has started working as a chauffeur ferrying around locals. She’s one of his regulars, and he thinks she’s sweet on him, which pleases Hale. If “we mix these families together,” he tells Ernest, Mollie’s money “will come to us.” As he often does, Ernest looks utterly baffled by his uncle.As Mollie walks toward her house, a pulsing bass line revs up. The soundtrack includes original music by Scorsese’s friend and frequent collaborator Robbie Robertson (who died in August), as well as old songs like the jumpy blues number that’s playing when Ernest and Mollie first meet in town. The notes that begin pulsing now create an entirely different mood and feeling simply because they sound like a heartbeat, if one that sometimes skips. And for good reason: The song is “Heartbeat Theme/Ni-U-Kon-Ska,” the meaning of which becomes clear when, after a few more cuts, the camera settles on Ernest’s face. “I am an Osage brave,” he says in halting voice-over, his words creating an odd counter-rhythm to the thumping.Apple TV+Ernest’s voice-over continues as the movie cuts to a brief bird’s-eye view of him pulling away from Mollie’s house followed by a close-up of his hand holding an opened illustrated book. Scorsese — working with his longtime editor, Thelma Schoonmaker — holds on the shot long enough for you to scan both pages, the chapter heading (“Osage Culture & History”) and the simple illustrations, including of a woman near a tepee, some men dancing around a fire and others on horseback. As Ernest speaks, he turns the page, revealing other images — a buffalo hunt, a map of Indian Territory — and it becomes clear that he’s reading, either aloud or in his head, from this book. Ni-U-Kon-Ska, he says, means “children of the middle waters.”Titled “Lilly’s Wild Tales Among the Indians,” the book belongs to Hale, who had earlier instructed Ernest to school himself on the Osage. It resembles the kind of old-fashioned children’s primers from the 19th and early 20th centuries that were still floating around the New York City school system midcentury, so it’s easy to imagine that a book like this drifted into Scorsese’s life at one point. (The main illustration in the movie is based on one such volume from 1901.) The book is as crudely simplistic as you would expect, yet when Ernest reads the words, “‘Move,’ said the Great White Father, from Missouri, from Arkansas, from Kansas,” he is also speaking to the grimly true history that informs Scorsese’s movie.Ernest reads a caption on an illustration, his finger tracing the words, “Can you find the wolves in this picture?” Just as he finishes the sentence, you hear the metallic jangling of a door opening, and the camera hurriedly pans up to find Ernest’s brother, Byron (Scott Shepherd) — in another light-colored hat — bursting into the room. “All right,” Byron says. “Let’s go.” The men rush to join a third, Blackie Thompson (Tommy Schultz), who’s waiting in an idling car. Ernest’s voice-over continues as they drive off, and a wailing harmonica joins the heartbeat, Ernest’s voice briefly dropping out when the men — now all wearing hoods over their heads — excitedly rob a wealthy Osage couple at gunpoint.The men convene at a billiard parlor (Scorsese is working fast!) where Ernest, as will be his habit for the remainder of the movie, makes a catastrophically wrong bet. “I love money! I love money!” he exclaims just before losing his night’s take. It’s first light when the men leave the parlor, and as they walk out Ernest’s voice-over resumes: “Dawn was always a sacred time for prayers.” The movie then cuts to a long shot of Mollie praying at a riverbank, an image that’s followed by a rapid volley of shots — of the sun, moon and fire — that ends on a vast green field dotted with the purple and white flowers that give the movie its title. It’s as if, Ernest says, Wah’kon-tah, the Osage word for God, had sprinkled the Earth with sugar candy.Although Ernest’s voice-over pauses during the robbery, it only fully ends when he and Mollie are at an outdoor christening, a nod at the life and the children they will soon make together. The strange heartbeat, though, continues as Ernest drives Mollie to her house, bringing the sequence full circle. This time, though, he walks Mollie to her front door, where she stops to give him the Stetson before they enter the house, where her mother is. Before they do, he puts on the hat. It’s preposterously large. It’s also a near-match for the pale 10-gallon hat that the John B. Stetson Company custom made for the silent-film star Tom Mix, a Hollywood hero who helped popularize the country’s romantic myth of itself that Scorsese furiously dismantles in this brilliant movie shot by shot, scene by scene, heartbeat by heartbeat. More