At the LFF: "Oslo, August 31st"

There is another Scandinavian filmmaker whose name is Trier, and his refusal to adopt the grandiose, mock-aristocratic "von" assumed by his Danish namesake Lars seems, in this instance, telling. The Norwegian Joachim Trier evidently goes about his business in an altogether more modest fashion: his debut Reprise snuck into UK cinemas in 2007, and its follow-up, Oslo, August 31st, is a film that considers depression, mortality and the end of things in a calmer manner than the operatic Melancholia. Low-key naturalism is this Trier's bag. The scenario of his latest - inspired by Pierre Drieu la Rochelle's novel Le Feu Follet, previously filmed by Louis Malle in 1963 - introduces us to Anders (Anders Danielsen Lie), a 34-year-old sometime writer and drug addict who, a day after making an unseen and unsuccessful attempt to drown himself, is granted 24-hour release from rehab to attend a job interview intended to get him back into society.

The interview will, it turns out, be brief, and not a notable success, so Anders uses the remaining hours available to him to conduct other business: tying up loose ends, reaching out. On a visit to an old acquaintance - himself a former party animal, now happily settled with a wife and child - a series of conversations see the two men kick over their regrets, their shared memories, and what-might-have-beens. Such encounters have the easy intimacy of many other cinematic walk-and-talks, but it's the leavetakings that prove backloaded with emotion: neither these old friends, nor really the audience, can be sure they're going to see a self-destructive drifter like Anders again.

Trier keeps subtly altering the film's tactics, which both keeps us on edge and better describes a character with no evident structure to his life: Anders is notionally free to go anywhere and do anything, yet he seems trapped within his head and body by a heavy-weighing despair. Around the halfway point, with afternoon turning to dusk, the film simply sits down alongside him in a cafe, and as Anders observes the passing foot-traffic - seeking out fellow travellers: not, perhaps, the students making optimistic plans for the future, more likely the mopey old souls heading into the night outside - so too Trier follows these characters with his camera, in the process swerving past those accusations of solipsism that dogged Melancholia, and sketching a deft portrait of life going on with or without the presence of his lead character.

And as the light begins to fade, so too the film becomes more episodic and scattered, individual scenes dissipating like shoppers from the city centre at closing time, here tuning into Anders' internal monologues, there leaving him entirely alone with his thoughts. In Danielsen Lie's perfectly pitched performance, this young man becomes a spectral figure - barely present, drifting mostly unseen through his contemporaries' parties - albeit one sharp enough to have gained some insight into his own condition. This is someone attempting both a reintegration with society and, one soon gathers, a reintegration of the self, gathering up the pieces of his life and seeing if there's anything there he might work with, that might provide him with a second chance, some reprieve.

Trier exercises cool control of the material, leavening this long, dark night of the soul with flashes of black wit and nocturnal beauty (Anders and his buddies take to their bikes at one stage, letting off fire extinguishers, and steam; they're freewheeling, much as the film is at this point); the final scenes inject a note of suspense, providing the protagonist with his best hope of happiness as dawn breaks, yet we've been left in little doubt that Anders has something deadly in his pocket, and indeed in his heart. After the Wagnerian sturm-und-drang of Melancholia, the younger Trier's film is destined to be found quieter - quietly optimistic, and quietly saddening - yet it gets to you no less. In its unshowy way, Oslo, August 31st is attempting a radical overhaul of recent cinema history, a project made clear by its own lump-in-throat coda: what if you remade Before Sunrise, only with a character who - in whatever company - is unshakably, inescapably alone?

Oslo, August 31st screens at the Vue West End on Wed 19 at 8.30pm, and again on Thu 20 at 12.45pm, before opening in selected cinemas from November 4.