The first thing you need to know about Quentin Tarantino’s Once Upon a Time… in Hollywood is that it is not a Charles Manson-murders movie, according to producer David Heyman.

“That’s one of the big misconceptions to clarify,” he tells EW. As part of EW’s Summer Movie Preview, Heyman and producer Shannon McIntosh, who’s worked with Tarantino for more than two decades, cleared up some mystery around the plot of Tarantino’s anticipated movie and teased some intriguing details.

Set in 1969, Once Upon a Time brings together Leonardo DiCaprio as fading Western TV star Rick Dalton and Brad Pitt as his stunt double Cliff Booth, two friends navigating an industry and era in flux, painstakingly re-created on location in Los Angeles by Tarantino. But Charles Manson and his deadly cult do play an important role in the film; Australian actor Damon Herriman plays the infamous cult leader, while Margaret Qualley, Dakota Fanning, and Lena Dunham play members of his Manson Family.

“It’s about the loss of innocence that came about in 1969 with the Manson family,” explains McIntosh. There’s the starry Margot Robbie as It Girl and eventual 
Manson-family victim Sharon Tate, who lives next door to Rick. “It’s the three classes of Hollywood,” says Heyman. “There’s the high Hollywood of Sharon, the declining star of Rick, and there’s Cliff, who lives farther out and with more humble means.”

But first thing’s first — pairing DiCaprio and Pitt together for the first time in a feature is one of the biggest draws of the project. For McIntosh, who worked with Pitt on Tarantino’s Inglourious Basterds and DiCaprio on Django Unchained, bringing the two together finally was “absolutely magnetic.”

“I can’t wait for the world to see Brad’s performance in this,” she says. “He’s so wonderful and charismatic and I think he is the Brad that people fell in love with years ago. Especially when he’s going toe-to-toe with Leo, his performance is amazing, he looks great and I think people will be reminded why he is the movie star that we know he is.”

And there’s an interesting dynamic between the two characters, Heyman explains. DiCaprio’s Rick Dalton is “not the movie star that he had hoped to be, so he’s struggling — he’s a working actor, but he’s not a movie star.” On the flip side, Pitt’s Cliff is “at ease, and comfortable with who he is” as Dalton’s stuntman.

“These are two people who have a history together and the loyalty that they have for one another is really potent,” Heyman says. “It’s really a film about that friendship and about the power of that friendship as they go on their journeys together and separately.”

And then there’s Robbie as the beautiful Tate. “[Sharon Tate] has been mythologized in some way through the murders but we get to see her as a person and we get to see her delight and enthusiasm and her sweetness,” Heyman explains. “She represents an innocence and innocence lost in some way, and that innocence is very much — that sweetness, that goodness, that delight with the movies, with her, with her life — is something that we experience.”

The role was prepared very carefully by both Tarantino and Robbie, who had the blessing of Tate’s sister Debra Tate. McIntosh said Robbie “wanted to honor Sharon’s memory and she really drilled down to make sure that she got the best performance and was really embracing all that Sharon was.”

She added that Tarantino “absolutely embraced Debra Tate, and that was very important to him and to us that she’d be comfortable with what we’re doing because obviously anyone thinking that we’re making it a Manson movie, which we’re not, but he was very sensitive to that and remains sensitive to that.”

But there’s also change afoot in 1969, a year that marked a major transition in Hollywood as it was shifting out of the Golden Age and with the expansion of television, into new, uncharted territory. For Rick and Cliff, it means a time for personal transformation as well.

“They’re going to have to reinvent themselves, and the extent to which they are able to will determine their futures. What I love about this, it’s just so singularly told because it’s Quentin Tarantino turning his eye on his hometown. Nobody else could have made this film,” Heyman says.

Los Angeles has always been home turf for Tarantino, and majorly featured in his first three films; Reservoir Dogs, Pulp Fiction, and Jackie Brown. But since then, he has traveled to further regions in his subsequent tales and it has taken Tarantino until this, his ninth film, to explore the Los Angeles of his childhood (he was 6 years old when the movie takes place) and the industry that so inspired him that he’s known to be a walking film encyclopedia.

“This is Quentin’s most personal film,” Heyman explains. “This is his memories of growing up in Los Angeles and being a fan of Hollywood.”

To transport audiences back to the Los Angeles of his childhood, Tarantino and his team transformed many of the city’s iconic locations on Hollywood Boulevard to their 1969 versions. There’s the renowned Grauman’s Chinese Theaters, the Aquarius Theatre on Sunset Blvd, and Sherman Oaks’ classic Mexican restaurant hangout Casa Vega. And there’s L.A.’s airport LAX, which Heyman quipped that they didn’t have to do much with as its 1969 self still pretty much exists today (and the airport’s renovations were held off until the film was done shooting, McIntosh added).

There’s also the music — the producers didn’t want to give away the magic of Tarantino’s soundtrack, but McIntosh said that KHJ, the radio station that dominated Los Angeles in 1969, and Boss Radio’s Boss Angeles will feature prominently as the characters travel through the story.

All of this culminates not only in Tarantino’s most personal film, but also his most moving one, Heyman says. It has his trademark sharp humor and style, but it’s “really moving, because it’s such a personal story,” the producer explains, drawing comparisons to Alfonso Cuaron’s Oscar-winning movie Roma.

Tarantino is deep into finishing the film for its July 26 release, but there have been discussions about whether it’ll debut at Cannes next month, 25 years after Pulp Fiction won the Palme d’Or, putting Tarantino on the map.

“We’re going to see if it’s ready,” Heyman says. “I know films are being announced, we have a little bit more time to decide. If we can get it ready, we will go. We’d like to go, of course, but at the same time, the film’s got to be all that it can be.”

Consider our appetite sufficiently whetted for Tarantino’s romp through the Hollywood of his memories.