For Quentin Tarantino, there has always been a special providence in the fall of an actor.

He’s built his career on featuring the slumping, the discarded, the overlooked — Lawrence Tierney, John Travolta, Bruce Willis, Pam Grier — and no matter how depraved the action on-screen, the genuine affection and generosity implied in the casting of a need-a-job old pro like, say, Robert Forster, always lend the movies an odd kind of warmth.

You feel that times 10 in his latest — and what Tarantino he says is his penultimate movie — Once Upon a Time…In Hollywood, a strange and loving ode to the TV/movie business in 1969, and a bit of a flip of the script for the director. Instead of casting a neglected actor in a starring role, he cast newly minted Oscar winner Leonardo DiCaprio as Rick Dalton, on the cusp of oblivion after a career in mediocre TV Westerns.

This is Los Angeles in its pre-blockbuster, pre-1970s configuration, a company town where vast machinery cranks out movies and programs that entertain the masses who watch with shared and synchronized enjoyment.

Tarantino regards this not so much as a Golden Age of Content — he was never one to fetishize the highbrow — but of employment. It’s an actor’s eye view of the business. His movie name-checks some famous icons and bygone industry practices (a marquee notes that Franco Zeffirelli’s Romeo and Juliet is in its eighth month in theaters). But Once really exists to celebrate the time when everybody — the fans and uncelebrated actors and agents and extras — gathered on Sunday night in front of the tube to watch shows like The F.B.I.

On special nights, a double episode.

The central figures in this movie are itinerant performers. There is Dalton, the once-popular ’50s TV gunslinger who is now scrounging guest-star work in other people’s shows. And there is his stunt double, Cliff Booth (Brad Pitt), who is Dalton’s best (only?) friend, driver (Dalton has been grounded by DUIs), and life coach, who urges his buddy on, both because he loves him (their chemistry is wonderful) and because he needs the work — he lives on the career crumbs that fall from Dalton’s meager plate.

A word here about the look (fantastic) and context (biographical mash-up) of the movie. Tarantino wants you to see it 35mm (there will be one local film print, at the PFS at the Roxy), and the special warmth of film does add luster to the director’s tender re-creation of neon/pop art Los Angeles. The carefully curated film is also is a living, moving museum of memory and memorabilia, and the older you are, the more intoxicated you will be by the references and the allusions (Mannix!). Also the more intoxicated you’ll be by the forms of intoxication — this was an age when men drank whiskey sours (how good they look on film!) and wore long pants.

Tarantino’s characters are sometimes historic, sometimes concoctions, sometimes a mixture — in Dalton and Cliff we see bits of Clint Eastwood, Burt Reynolds and Hal Needham. (One man’s backstory invokes the suspicious and unsolved death of Natalie Wood, a bit tactlessly.)

Dalton’s career also traces the faltering fortunes of the Western, losing its hold on the American imagination. Shows like Dalton’s fictitious ’50s hit — Bounty Law — were a training ground for guys who’d go on to become Eastwood and Steve McQueen (played here by Damian Lewis), while others went on to remain Rowdy Yates.

Tarantino dangles Dalton between fame and obscurity. In Once, Dalton, contemplating a last-resort move to Italian Westerns, has a lot riding on his supporting role in a particularly ambitious episode of Lancer (this was an actual show, and Timothy Olyphant appears as lead James Stacy). DiCaprio has some good scenes here as a desperate man, summoning what’s there of his talent, to prove something to the business, and maybe to himself.

Meanwhile, Tarantino follows the parallel story of Booth, whose flirtation with a Charles Manson cult member and hitchhiker (Margaret Qualley) leads him to their lair — the abandoned Western movie set known as Spahn’s ranch, now overrun with Manson’s followers (two of them played by Lena Dunham and Dakota Fanning). Cliff’s interlude at the ranch is also presented by Tarantino as a kind of Western drama — Cliff on the streets of the back-lot town where he used to do stunt work, in a showdown with the strangers who now occupy the place.

We know these stories — Dalton, Cliff, the cultists — will all converge. One of the first things Tarantino shows us is that Dalton lives next-door to Roman Polanski and new bride Sharon Tate (Margot Robbie), at the Cielo Drive address where history tells us Tate and two others were murdered on Aug. 9, 1969.

It’s important to note that Tarantino isn’t much interested in Manson (who’s barely on-screen), or the demented principles of his cult. The Manson women register as a kind of menacing symbol — a threatening presence in bustling L.A., in part for their indifference to its sprawling moviemaking apparatus and its place in culture. Usurping old movie sets, marching heedlessly past the James Dean and Hitchcock murals, they represent something that Tarantino finds especially ominous and alien — people who don’t love movies, or care about their history.

The director, on the other hand, is interested in Tate. Robbie’s is not a gigantic part, but it’s important — and she stands in the movie as a kind of mirror image to Dalton’s fading star — she’s the It Girl ingenue with the hotshot director husband, and the gated doors of Los Angeles are opening to her.

She’s thrilled to be a part of it, thrilled to be working — one sequence follows her into a matinee showing of her Matt Helm movie The Wrecking Crew — she watches in a kind of rapture, enjoying her own performance, remembering the work she put in, enjoying even more the audience response to her work (you can also feel in these moments the finding-magic-in-junk thrill that animates Tarantino).

These scenes have an edge to them, given what history records of her fate, but the way Tarantino presents the events of Aug. 9 reflects his instinct to treat gently the forgotten actors of yore, and is certainly in keeping with the Once Upon A Time prompt right there in the title.

There are garish spasms of violence, to be sure, and many, especially those targeting women, felt to me like a misstep — ditto the self-absolving commentary about movie violence that Tarantino builds, rather clumsily, into the script at this crucial moment.

But there is a lot to like here, a few things to love. Like the fact that someone in Hollywood can still assemble a cast this large and impressive — someone who does not work for Marvel.

Once Upon A Time...In Hollywood. Directed by Quentin Tarantino. With Leonardo DiCaprio, Brad Pitt, Margot Robbie, Margaret Qualley, Timothy Olyphant, Al Pacino. Distributed by Columbia Pictures.

Running time: 2 hours, 39 mins.

Parents guide: R (violence)

Playing at: Area theaters