Rick, a sloppy drinker and a furious smoker, wears his feelings close to the surface. He weeps aloud over the state of his career, throws an epic tantrum in his trailer when he messes up a scene and is moved to tears by the exquisiteness of his own acting. Cliff is a different kind of cat — lean, taciturn, self-effacing, slow to anger but capable of serious violence. Some say he’s a murderer; he himself occasionally alludes to a criminal past. Better not to ask. Apart from Rick, his main attachment is to his dog, Brandy, whose loyalty is the mirror of his own. (DiCaprio’s baroque, exuberant emotionalism perfectly complements Pitt’s down-to-the-bone minimalism. They’re both terrific.)

If the guys aren’t quite Don Quixote and Sancho Panza, their companionship nonetheless takes shape within a fundamentally aristocratic social order. Joan Didion, in an essay first published in 1973, described the Hollywood of that era as “the last extant stable society,” and Tarantino’s tableau confirms this view. Life isn’t perfect, but it is coherent. People know their place. They respect the rules and hierarchies. Rick’s neighbors, Sharon Tate and her husband, Roman Polanski (Rafal Zawierucha), live higher up in the canyon (at the end of a gated driveway) and also on the status pyramid. They are regarded not with envy or resentment, but with awe.

The governing virtue in this world is courtesy. The things produced within it are ridiculous, but also beautiful. Residents take seriously things that are objectively silly, which lends a measure of charm to otherwise pedestrian moments. A series of on-set interactions between Rick and two other actors — a leading man played by Timothy Olyphant and a juvenile played by the phenomenal Julia Butters — demonstrate the workings of this code. What they’re collaborating on might look like disposable commercial trash, but making it involves craft and tradition, folk wisdom and spiritual discipline, trust and integrity.

Tarantino’s sense of the movie past is often described as nostalgic. He tends to be seen — by admirers and critics alike — as a film geek, a fanboy, a fanatic cinephile with an encyclopedic command of archaic styles and genres. True enough. But “Once Upon a Time … in Hollywood” shows that he deserves a loftier, possibly more contentious label. It’s the expression of a sensibility that is profoundly and passionately conservative.

John Ford, one of old Hollywood’s greatest conservatives, ended one of his greatest movies with the exhortation to “print the legend.” Tarantino’s answer is to film the fairy tale.

Alongside the knight and his squire, there is a princess — Tate — who lives in something like a castle and is married to a man who looks a little like a frog. Tarantino has never been much interested in sex or romance — violence and vengeance are what makes his stories run — but he has a sentimental investment in marriage and a thing about wives.