Full spoilers follow.
For most of its length the film withholds a plot. Rick Dalton grinds through a guest-villain role on a Western TV series, has a career-crisis conversation with a casting agent, does a stint of Italian pictures and returns with a new wife and no money for a stunt double. Cliff Booth, meanwhile, accumulates the film's strangest detours: a comic sparring match with Bruce Lee, and a trip to Spahn Ranch — a decayed Western set he once worked on — where he finds it squatted in by Charles Manson's followers. All of it runs beneath a dread the audience supplies itself, because everyone knows what August 1969 on Cielo Drive means.
Then Tarantino breaks history. On the night the real murders occurred, the Manson followers driving up the hill are provoked by a drunk Rick, and in the film's decisive swerve they decide to kill the man who taught them violence on television instead of going next door. They enter Rick's house rather than Sharon Tate's. What follows is the film's eruption of brutality — Cliff, high and accompanied by his dog, dismantles the intruders with a savagery that critics found either cathartic or unbearable, and Rick finishes the job with a flamethrower salvaged from one of his own movies. The gag is exact: the actor is finally saved by a prop from the trash of his own career, and the film's fake violence destroys the real thing.
Sharon Tate survives. She and her friends are alive inside the gate, and the last beat is a neighborly exchange up that driveway — Rick, absurdly, invited into the world he has been watching from the other side of a fence. The murders never happen.
What this retroactively reveals: the title was the contract all along. This is a fairy tale, and the entire three hours of loving reconstruction — the real Cielo Drive, the Ektachrome home-movie footage, the archival footage of the genuine Sharon Tate watching her own film with a laughing audience — exists to make the wish specific enough to hurt. Tarantino's alteration functions as a corrective for Tate, restoring her as a person instead of a crime, and as a demonstration of cinema's power to alter reality: the director snips the frame he cannot bear out of the print of the past. The Spahn Ranch sequence gains its meaning in hindsight too, as the film's diagnosis — the dead Western myth and the killers nesting inside it — and Rick's earlier despair about becoming useless is answered with the one thing history never offered: a second chance handed to a man who did nothing to deserve it. The ending's divisiveness is structural, not accidental: the same excess that delivers the catharsis also exposes the appetite behind it, which is why some read the finale as the Tinseltown dream being demolished rather than rescued.