What does it take for a seemingly normal person to become a star – to create something that captivates our collective imagination? I feel like every musical rise-to-fame story – including this year’s Bohemian Rhapsody and A Star Is Born – is having a go at answering this question. The subversive answer that 30-year-old writer-director Brady Corbet gives in his new movie Vox Lux is, in two words, ‘unimaginable horror’.

Vox Lux follows Celeste (Raffey Cassidy, who you might recognise from a similarly haunting performance in The Killing of a Sacred Deer), a 13-year-old girl who survives a school shooting in the film’s deeply disturbing opening, set in 1999. With a bullet permanently lodged in her spine, she recovers slowly, spending time with her sister Eleanor (Stacy Martin). Together the pair write a song to capture her emotion, which Celeste sings at a tribute to her massacred classmates. A TV camera captures the whole thing, and The People love it. “It was not her grief, it was theirs,” muses Willem Dafoe’s detached, mythical-feeling Narrator. Something in Celeste grips the public, and she becomes a star, signing a deal with a perfectly sleazy manager (Jude Law). We see her catapulted into the world of celebrity. An album is recorded in Stockholm, a one-night-stand is had with a heavy-metal frontman, two planes hit the World Trade Centre, and then we jump 17 years forward.

Celeste is now played by Natalie Portman, with outlandish fashion and make-up and a fuck-you attitude: she’s turned into a fully-formed pop star, an icon. This second act opens, however, with a mass shooting on a beach in Croatia, in which the perpetrators wear the same sparkling masks that featured in an early music video of Celeste’s. From here, the rest of the movie is a whirlwind day-in-the-life of present-day Celeste, as she conducts interviews in the wake of the attack, tries to spend time with her daughter (a conspicuous second role for Raffey Cassidy), has a few tantrums, and rushes towards the debut live performance of her newest album.

This struck me as a really intriguing character to build a movie around. I don’t know if I could fault the first act at all, really: all of the young-Celeste stuff is engaging, dynamic and original, with a winning ambition to it. To wit, it’s the kind of thing you don’t see enough of in modern Hollywood, and even if I hadn’t liked it as much as I did, I’d still be glad it exists. The school shooting sequence is gripping, and it might be the first one I’ve seen where the shooter genuinely just feels like a kid with a gun. It’s really disturbing. From there Corbet works with Cassidy’s reserved, vulnerable, deer-in-the-headlights performance to deliver a really moving portrait of lingering trauma. Cassidy’s Celeste is taciturn, with a lot of pathos. She parts with her reticent demeanour only occasionally, reminding us of the weight of what she has been through: “You make the sort of music the boy who attacked me used to listen to,” she nonchalantly tells her one-night-stand. It’s a particularly unsubtle ironic reveal when we later learn that Celeste’s daughter was conceived that night.

There are plenty of these really showy, bombastic choices here (the title card as we begin Celeste’s story reads “Genesis 1999-2001”), but I actually go in for all of them. The Willem Dafoe narration and its mythical, once-upon-a-time vibe actually works really well as a stylistic anchor – it lends a kind of gravity and dramatic import to this grounded 21^st-century story, and it’s just really fun to listen to. There are also a few moments when, as Celeste is entering into the pop-stardom machine, we just get these exquisite cityscape shots, cut together with loud, pounding, ominous music. It’s postcard scenery turned threatening, industrial – a great visual metaphor for the commercial world tightening its grip on Celeste and her pure, as-yet-untainted talent. In fact, all of Lol Crawley’s gorgeous cinematography has this same casual sense of menace to it: the camera’s always a little close to its subject, not so much watching Celeste as it is bearing down on her. It’s grandiose, unsubtle stuff, but the boldness is refreshing, and it works.

Then we jump to the present day, and Corbet kind of loses me. We get a new title card, “Regenesis 2017,” and the movie suddenly takes those kind of bold, in-your-face directorial choices and turns them up to eleven – it’s here that they start to bother me. The grandiloquent tone becomes melodramatic. The sinister cinematography and score stop being dynamic and start feeling predictable. And having Cassidy play Celeste’s daughter, when we’ve just seen her as young Celeste, inherently draws attention to itself in a way that no longer feels self-aware: in-the-moment affectation and shock seems to become the goal, instead of cohesive style.

Meanwhile, taking over the lead role, Portman is absolutely going for it, and the performance doesn’t quite work for me. She’s doing a particularly hammy New York accent, and her Celeste is brimming with energy; loud, larger-than-life, and almost aggressively unapologetic. This Celeste is an alcoholic and a drug abuser, who feels like she’d fall apart any second if not for her manager, her family, and the other people in her support system. You can’t help but think of the old aphorism that celebrities remain the emotional age at which they become famous. But in fact, where Cassidy’s Celeste felt mature beyond her years, Portman’s version is temperamental and brat-like. Celeste hasn’t just had her emotional growth stunted, it has actually regressed. The difference didn’t feel natural to me, though. If anything it was grating: the most tangible link between the two versions of Celeste is her predilection for chokers. Unlike Cassidy, Portman just feels like she’s in the wrong movie. Her performance isn’t quite serious or severe enough to gel with Corbet’s grandstanding direction, and the character doesn’t strike me as particularly different from any other product of fame I’ve seen in fiction. What happened to Celeste’s uniquely traumatic past? It’s like the film cast aside its distinctive, fascinating setup and decided to just do a price-of-fame character study. There was an element of that in the first act, for sure, but what made Vox Lux exciting for me was the intersection between that element of Celeste, and the trauma in her past. It’s wasted potential.

What does come into clarity in “Regenesis”, though, is one particular Hot Take from Corbet that’s bound to attract attention. In one of Celeste’s interviews, we’re pointed towards a link between the motivations of pop stars, and domestic terrorists. That’s to say, not Al-Qaeda or ISIS, but school shooters like we saw in the start of the film – the kind of home-front attackers who don’t pursue a religious agenda, but instead some kind of mass infamy, or revenge for a perceived wrong. I get the point – the drive to be seen creating a spectacle is something these two groups have in common, and the tendency of both stir up the media is palpable. It’s truly a wild point to make, and I would’ve been interested to see where Corbet took it, but he kind of doesn’t.

The film lands, instead, on a final musical performance to an adoring crowd (again recalling A Star Is Born and Bohemian Rhapsody). Hilariously vague phrases like “BABY AVEC CASH” are blasted onto a screen behind Celeste as she sings and dances in a huge spectacle, the songs for which were all composed by Sia. Nabbing the songwriter behind ‘Diamonds’, ‘Pretty Hurts’, and of course ‘Chandelier’ and ‘Cheap Thrills’ is a massive get for this film, and so the songs are, of course, fantastically catchy. It makes for a great ending, one into which you can kind of read anything you want, but I can’t help but mourn for the film I saw coming together in the first act. There’s plenty of meat on the bone of exploring Celebrity Culture, but there’d be a lot more in the fascinatingly weird, memorably original violence-trauma-pop angle the film seemed to be taking earlier on. Vox Lux wants to be a fresh, striking, subversive take on our culture right now, and I wanted it to be that too, but it’s not. Not quite, anyway.

Vox Lux is in cinemas from February 21^st.