Dir: Lee Chang-dong. Cast: Yoo Ah-in, Steven Yeun, Jeon Jong-seo. 155 mins

Burning, which could easily emerge as this year’s Palme d’Or favourite, is the first film in eight years from South Korea’s Lee Chang-dong, a director whose challenging, ambiguous films – Oasis (2002), Secret Sunshine (2006), Poetry (2010) – are the kind that grow and grow in the mind afterwards.

That rule particularly applies here, because of a skin-crawling climactic scene, brilliantly orchestrated, which bathes every previous one in a chilly, but retrospectively-there-all- along, new light. What precedes is a study of buried class conflict in contemporary Seoul, of unspoken rage, palpable alienation and sexual longing. But it keeps a remarkably tight lid on all these simmering themes, until the shocking eruption in store.

The film’s mysterious immensity is especially striking given the source, “Barn Burning” – a typically refined, 10-page short story by Haruki Murakami, with the same title as one by William Faulkner. Lee has built a carefully modulated story of his own around Murakami’s matchbox of an idea, about two rival suitors, one of whom makes a strange – and not necessarily trustworthy – confession about arson.

The main character is Jongsoo (Yoo Ah-in), a young, working-class guy from a farming background, whose father, who never speaks, is in and out of courtrooms, because of a repeated pattern – this comes from Faulkner – of vengeful and violent behaviour.

At the very start, Jongsoo meets the forward, impulsive Haemi (Jeon Jong-seo) at a raffle on the street, and she says she remembers him from a childhood episode when he rescued her out of a well. Jongsoo can’t remember this at all, but shows no objection when Haemi invites him back to her small flat, on the pretext of feeding her cat.

Tenderly, and clumsily, they have sex, in a touchingly awkward sequence that’s characteristic of Lee’s skill for enchanted realism. Whatever we feel about Jongsoo at this stage, though – he gazes mysteriously during the act on a sunbeam, reflected off the Namsan Tower, that brightens Haemi’s room just for a brief moment each day – is going to mutate unpredictably as the film proceeds.

The same is true of Haemi, who abruptly departs to Kenya on a two-week trip, leaving Jongsoo listless and underoccupied. The cat, which he returns to try and feed, never makes an appearance, just as Jongsoo’s father is perpetually absent from their run-down farm. And Jongsoo’s idea of keeping his own company, which he often has no choice but to do, is pretty unsettling, tending towards masturbation – eyes fixed on that tower out of Haemi’s window – and an alleged writing project we barely see him bothering with at all.

Jong-seo Jeon in Burning

The story gains a crucial third character when Haemi sweeps back from Kenya, having been thrown into a three-day airport crisis and thereby met Ben (Steven Yeun), a well-to-do yuppie who accompanies her, much to Jongsoo’s obvious dismay, when she comes through arrivals. Whatever Jongsoo’s assumptions were about any potential with Haemi, they’re thrown into disarray, and though the new couple make a pointed effort to hang out with him, visit, and smoke weed, his third-wheel status is cringingly obvious.

There are parallels with Patricia Highsmith’s Ripley books here, particularly in the envy and resentment Jongsoo feels towards Ben, who has a fabulous wood-panelled apartment in the middle of Seoul, a sportscar, and an affable if bored air: twice we catch him yawning distractedly at social events. This film’s Jay Gatsby or Dickie Greenleaf, he’s given a lot of smiling poise by Yeun – a Korean-American star on the rise – and a facade of unrufflable bonhomie which makes him Jongsoo’s secret nemesis.

Ben is described by Haemi, whose feelings towards him are quite opaque, as just being one of those indefinably rich people who can do whatever they want – even if it’s a hankering, unknown to her, and for which the film provides no evidence but his own say-so, for burning down greenhouses in the countryside. The contrast with Jongsoo, mucking out cow stables, because he must, in a state of manic exasperation, could hardly be any clearer.

Steven Yeun in Burning

The daring of the film is how rudderless, desperate and slow-witted Jongsoo, played so very discomfitingly, becomes as a protagonist, while he scrabbles around to get a grip and convinces himself that he’s fallen in love. Haemi, given to impromptu moments of performance art, such as peeling imaginary tangerines, is not without her own damage.

In the film’s most beautifully composed and emotionally pregnant sequence, she dances to Miles Davis, stoned and topless, with the sun disappearing behind trees at Jongsoo’s farm. As the light fades, she starts to cry, and it’s not long before she will vanish yet again.

This is Lee’s closest ever film to a thriller, but it defies expectations, offering multiple, murky solutions to a set of mysteries at once. The mystery of the cat is maybe-or-maybe-not solved. Haemi may have voluntarily departed, or been killed. Ben may be a sociopath, a liar, or both.

The only clarity, in a perverse way, comes in the irreversible last shot, as if everything that has vexed, confused and thwarted Jongsoo could be symbolically torched to purify his soul. But it’s a black place inside. The sun has gone for good.