Edgy. That’s perhaps the best word to sum up Todd Phillips’ Joker – a DC Comics spin-off that serves as a solo origin story for Batman’s most enduring nemesis. And we’re not just talking about the film’s controversial new angle on a well-worn villain, nor the fervent online debate it has provoked since its premiere at the Venice Film Festival, where it picked up the coveted Golden Lion award.

No, we’re talking about the film itself. The remarkable thing about Joker is just how on edge it makes you feel, thanks to a palpable sense of unease that’s sustained throughout its relatively lean two-hour running time. From the moment the film begins, with a ‘70s-style Warner Bros logo giving way to an extreme close-up shot of a tormented clown forcing a smile with a single tear running down his cheek, it’s clear that this is not your typical comic-book movie. (We’re deliberately not using the other oft-used term for the genre; there are no heroes here.)

That clown is Arthur Fleck (Joaquin Phoenix), a “mentally ill loner” who lives in a crummy apartment with his ailing mother and works as a jobbing jester, plagued by a neurological condition that causes painful, uncontrollable fits of laughter. He ekes out an existence in a Gotham City that’s suffocating under piling-up mountains of trash and overrun by “super rats”, in which a rising wealth gap has stoked anger and resentment – leaving law and order teetering on a knife edge.

Kicked while he’s down again and again, be it literally by a gang of street thugs calling him “freak”, or figuratively – thanks to a failing health system that deprives him of his meds, and a series of events that sees him losing his day job – Arthur’s only escape is his fantasy of becoming a stand-up comedian, inspired by his late-night television idol Murray Franklin (Robert De Niro).

But it’s not just tensions between rich and poor that are reaching boiling point – the demons within Arthur are threatening to spill over, too. “Everyone is awful these days,” he says. “It’s enough to make anyone crazy.” So when Arthur finally snaps, his growing disdain compounded by a loaded gun, the two worlds collide violently – kicking off a movement that enables Arthur to be reborn as the future Clown Prince of Crime. As one of his onscreen predecessors once so memorably put it, all it takes is a little push.

Like we said, this isn’t your typical comic-book movie; in fact, it’s unlike anything the genre has produced before. Joker is a gritty character study of a dangerously damaged man, more in the vein of early Martin Scorsese movies – as has been widely discussed already, it contains particular shades of 1976’s Taxi Driver and 1982’s The King Of Comedy. It’s bleak, tightly wound, and permeated by jolting bursts of shocking brutality. And at the centre of it all is an extraordinary, transformative turn from Phoenix. At first eliciting pity and, by the film’s second act, repulsion, his tortured, twisted performance provides Phillips’ fable with a terrifyingly unpredictable linchpin. Not only is it a career highlight for Phoenix, but it more than holds up against Jack Nicholson and Heath Ledgers’ iconic Jokers past.

The world-building is great, too. This Gotham isn’t the gothic cityscape of Tim Burton’s Batman movies or the modern metropolis of Christopher Nolan’s The Dark Knight Trilogy, but a new version inspired by Scorsese’s old stomping ground – the mean streets of ‘70s/‘80s New York (while a date isn’t explicitly mentioned, Joker certainly emulates that time period). It’s a carefully crafted shithole: a lived-in world that feels dirty and oppressive; old-school and yet, despite the lack of smartphones and LED screens, surprisingly relevant. It’s different, yes, but not that different: Gotham has often been depicted as a dump – one that, in Bruce Wayne’s eyes, has always been one worth saving. But this is not Batman’s worldview, and the film’s design reflects that.

In fact, while Joker is undoubtedly a standalone project, it doesn’t totally shy away from its comic-book origins or the wider Batman mythos. Phoenix’s villain might not be the Joker we know, but he grows to embody his essence, especially as his character moves ever-closer towards discarding Fleck and embracing the green-haired menace. One brilliant, claustrophobic scene set inside a subway carriage full of angry protestors sees him become the masterful orchestrator of chaos that we’re all familiar with; likewise, his constant assertions that he’s not politically motivated hint at the anarchy that’s to come.

It’s here that things get a bit iffy, though. Given the fact that this film is going to invite difficult conversations, it’s not massively clear what, if anything, it’s trying to say. The main problem is Phillips’ reverence of his filmmaking hero, which proves to be a double-edged sword. Joker wears its cinematic influences on its sleeve, perhaps a little too much – from the grubby urban setting to the scenes of a topless, spindly framed Phoenix acting out his delusions in front of his telly, Joker isn’t so much inspired by Scorsese as actively aping him. This might make it a comic-book movie like no other, but the film ultimately lacks the strong, auteur-style voice of Marty’s classics.

Aesthetics (and composer Hildur Guðnadóttir’s mournful score) aside, the movie as a whole doesn’t quite match up to the brilliance of Phoenix’s powerhouse – and likely awards-grabbing – performance. Still, it’s not far off: thrilling and unsettling in equal measure, Joker is a film that thrives on the edge – and that’s what makes it so compelling.

Joker opens in UK cinemas on 4 October.

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