Cloud (Tosawart) is a hired assassin working to support his HIV-positive mother (Silapran) and brother Fog (Srimalai). But when he's asked to kill Stone (SangThong), he kidnaps him instead. As they escape, Cloud is shot, and it's Stone who nurses him back to health. After lots of aching glances, they finally give in to their mutual lust, but quickly separate in a flare of self-loathing and embarrassment. With Stone back home, his fiancée Sand (Rujinanoun) knows something is up.

The story continues over 25 years, as these two men pine over each other while their personal lives implode. It's overwrought on every level, with huge passions and quiet sobbing. Cloud's family situation gets increasingly messy, simplistically explained away by a story about the boys' evil stepdad (Ayudthaya) as Cloud heads for a Taxi Driver-style cleansing shootout with the mob. Meanwhile, Sand gets increasingly jealous, and eventually picks up a gun to cause even more emotional turmoil. All accompanied with a soundtrack that blends tearning vocals, swelling violins and Miami Vice-style pulsing.

Visually it's fantastic, with big action sequences that are lushly photographed through slo-mo rainfall. Much of the screen-time consists of sweat, skin and muscle, as the men mope on rooftops wearing just their boxers, staring into sumptuous skies. But with dialog this trite, it's impossible to engage with them at all. And the plot's histrionic structure makes their actions and reactions deeply annoying. Why is Cloud so cold-hearted? Why is Stone so pathetic? Even though theirs is a forbidden love, can't they just snap out of it?

As it progresses, the film starts to drift aimlessly, the pace falters and filmmaker Arnon tries to make up for it by cranking up the distraught musical score. It's fascinating to see such tough characters in a gay-themed Thai film (usually they centre on ladyboys); this is essentially about two straight men discovering an unexpected desire for each other. But by over-stressing the important themes, the film becomes both silly and boring.

Alvaro (Román) is a long-time resident of a marshland community in which everyone gets involved in everyone else's business, including gossiping about the "official" reason a local boy died. But Alvaro maintains a quiet detachment; besides is old reed-farmer friend (Muñoz), he only deals with the passing missionaries and loggers when he needs to. In this macho society, he has to keep his sexuality secret from his neighbours. But Turu (Valenzuela), who captains the waterbus El León, suspects something, and things flare up after Alvaro criticises him for a homophobic rant.

Filmmaker Otheguy creates a wonderfully realistic and otherworldly tone out of this setting, with people living their lives hiding behind trees, separated by the water on which boats are constantly prowling. Gorgeously shot in textured black and white, the steady river current and gentle wind rustling the leaves make up for the inarticulate characters. There's very little dialog, but then these people have little to say to each other. And the film's style beautifully highlights their internal rhythms against their watery environment.

And the loneliness is almost overwhelming. These people are isolated both physically and emotionally, and they're also all in denial, refusing to accept the realities of the world around them. They'd rather maintain an illusion of calm stability. In many ways, this fantasy of propriety has always been there, and it's always been a mask for the racist, xenophobic and homophobic turmoil that's just under the serene surface.

The actors play these people with remarkably subtlety, conveying the characters' inner attitudes with the smallest gestures. Even so, these people are so aloof and quiet that we never quite get to know them, Alvaro included. This leaves the film feeling random and anecdotal, with disconnected scenes that seem irrelevant or elusive. But in the tiny details, we can immediately identify with these people, as the almost surreal setting becomes an introspective and challenging portrayal of every community on earth.

• BEST SUPPORTING ACTOR:
Jérémie Renier

After her divorce from Luc (Descamps), Pascale (Huppert) got the house and the twin sons (played by the Renier brothers), who are now fully grown adults, even though they act like children. Thierry (Jérémie) is stubborn and self-centred, while François (Yannick) is helpful and dependent. Both of them are shocked to find out that their mother is planning to sell the house to open a B&B with her new boyfriend (Cuppens), but it's Thierry that digs his heels in, leaving François to watches helplessly as his mother and brother wage all-out war.

There's a creepy realism to this central trio of characters that prevents us from looking away from the screen. This is a mother who has indulged her sons all their lives, leaving them unable to function as normal adults. And their father is no help, making things worse by encouraging their rebellion. The Reniers recreate the twin bond with astonishing authenticity (in real life, Yannick is six years older); these are very different young men who are as close as brothers can be, and yet also wary of each other.

Meanwhile, Huppert is riveting at the centre of the family hurricane. She's trying to take control of her life, but it seems like everything and everyone is conspiring against her. And to be honest, she doesn't help her cause much. Not one of these characters is particularly likeable, except perhaps the outsiders (Cuppen's nice-guy chef and Lubansu as Thierry's gym-trainer girlfriend) who are burnt by the flames of this family from hell.

Director-cowriter Lafosse may not seem to have a discernible point, but his examination of the jagged edges of family relationships is dead on. These are people who love each other deeply, and yet are increasingly unable to share a house. We can understand why Luc has chosen to start over, giving the boys his money rather than his affection. And we can understand why Pascale just wants to throw them out of the nest to fend for themselves. In the end, it's not particularly hopeful, but it's frighteningly real.

We first meet François in 1955 at age 14 (Dubuis), when he begins to discover his family's dark secret. We also see him coping with the ramifications at age 37 (Amalric) and as an insecure 7-year-old (Vigourt) with an imaginary brother and no idea that his parents (De France and Bruel) have never told him the truth about their war-time past, including relationships with a brother and sister (Plagnol and Sagnier), and their true ethnic roots. All François knew was that he never lived up to anyone's expectations.

Miller approaches this complicated story with a dreamy editing style that flicks around the story, from long before François was born to the present-day (which is shot in black and white). Each scene bristles with realism, offering telling details and plot-redefining information that coalesce into an epic story of love, betrayal and deception. But the complicated, crowded plot makes it hard to find an emotional centre we can fully engage with.

That said, the cast is extremely strong, pouring energy and passion into their performances. And there's plenty of melodrama to chew on, what with illicit longings, dangerous curiosity and moody self-doubt on every side. And the film's rich themes add to the characterisations, as they deal with a sudden surge of bigotry and prejudice in their previously easygoing society. And when jealousy flares up suddenly, there are some strong, wrenching scenes that follow.

It's also fascinating to watch these characters try to navigate the Nazi occupation of France from a distinct angle we don't often see on screen--complex, balanced, difficult to pigeonhole in any way. With skilful camera work and cleverly gritty production design, Miller beautifully captures the impact the war had on everyday people caught up in terrifying circumstances that forced them to react in a wide variety of ways. And how everything that happened continues to haunt their lives as well as the generations that follow.