Robbie’s portrayal of Tate was a core component of my experience of this movie, and this article will tell you why. But I can see why it left a lot of people cold: Tarantino assumes a lot of prior knowledge about 1960s Hollywood. There are essential facts, crucial to the story, that will radically alter your understanding of the plot. And these facts aren’t given to you at any point during the movie. You’re either an insider or an outsider. And only insiders can see what Tarantino is attempting with Robbie.

Tarantino responds to the criticism of the silent Robbie by saying: “she is an angelic presence throughout the movie, she’s an angelic ghost on earth, to some degree, she’s not in the movie, she’s in our hearts.” When I saw the movie I understood exactly what he meant: Because I know all about the Manson Family. I know that, in 1969, young members of a psychadellic cult break into Sharon Tate’s home while she’s 8-months pregnant and murder her and her five friends.

As a result, when I watched Sharon Tate in this film, I watched with dread: it was like I was watching a dying woman’s final hours.

I came to understand the criticism when I saw the movie a second time. This time I went with my friend Jack. Jack is a few years younger than me and doesn’t know anything about this era of Hollywood. He doesn’t know who Sharon Tate was, has never heard of Roman Polanski, or Steve McQueen, or the Spahn Ranch. Jack has heard of Charles Manson. And while he is portrayed by Damon Herriman, a dead ringer for the cult leader, Herriman is on screen for one scene which is less than a minute long, and is never referred to onscreen as anything other than ‘Charlie’.

Jack has no idea that there were real people in this film. And why would he? The film’s title card doesn’t indicate these events are based on a true story. And while Tarantino makes an effort to ground the film in reality by introducing 1960s movie celebrities, Jack had no frame of reference for any of this. He had no way to know which characters were real, and which were fictional.

Tarantino is a master of alternative histories. In 2009’s Inglorious Basterds, Brad Pitt’s crew kill Hitler in a cinema in 1944. This is an incredible step into the unknown: the plot departs from history, and everything in the film’s plot is to play for. And it’s unmissable: Everyone knows who Hitler is, and how he died.

In Once Upon A Time, this departure from history happens much earlier in the film, occurring at the start of the third act rather than the denouement. Leaving more time to explore this alternate timeline, and more time for Jack to get lost in a history he’s not familiar with.

The scene is set: Everyone is in their houses, the Manson family arrives in their car. However, the fictional Rick Dalton confronts the murderers, and they decide to kill him instead of Tate.

In the eyes of an insider, this is an incredible bend in the road. All of a sudden, we are off the map, and we are caught up in the thrill of the violence not only because of its spectacle, but also because the pregnant Sharon Tate’s life is at risk. Only Tarantino, with his reputation for graphic violence, could make me feel such dread. In the cinema I was wishing, really wishing, that I didn’t have to watch a pregnant woman get stabbed in the belly.

The incredible explosion of violence, while harrowing in its own way, is miraculous: even though Pitt’s Cliff Booth is stabbed in the leg, both his friends and the six innocent people next door, are spared.

However for Jack, and other outsiders, this miracle is totally lost. Jack didn’t understand the danger of Booth’s trip to the Spahn Ranch. He doesn’t feel the payoff of watching a day-in-the-life of Sharon Tate, because he doesn’t know her days were numbered. He doesn’t feel the miraculous relief of seeing Rick Dalton enter her home at the end of the film, alive and well. For Jack, the film is a series of Hollywood homages, culminating in a hurricane of violence, where nothing of importance is lost. (Because, of course, it’s that which is not lost which is so precious.)