Pororoca

While Three Billboards Outside Ebbing, Missouri, showing elsewhere in the programme at this year's San Sebastian Film Festival, considers the cocktail of rage and grief that has simmered in its protagonist Mildred's mind for months, Pororoca flips the idea on its head, showing the gradual creep of anger and loss from ground zero.

As you might expect for a film clocking in at almost two-and-a-half hours, director Constantin Popescu takes his time to set the scene - an idea which works well initially and, if it suffers longueurs at the midway point, ultimately pays off in that it makes the sudden speed with which the last act unfolds feel all the more shocking.

Tudor (Bogdan Dumitrache) and his wife Cristina (Iulia Lumânare) are Mr and Mrs Average, living a comfortable middle-class life with their seven-year-old son Ilie (Stefan Raus) and his five-year-old sister Maria (Adela Marghidan). Popescu lets us get a feel for the relationship, essentially a picture of normality.

It is on a day like any other, when Tudor takes the children to the park that tragedy strikes. It's not that he's doing anything wrong, he's paying attention to the pair in between phone calls, dishing out water to them, chatting to another mum about getting one of them an ice cream and generally letting them burn off some energy with the other kids. But suddenly he realises he can't see Maria. This is not only every parent's nightmare but a feeling that most people who have had to look after kids for any amount of time will understand - the sudden heart-stopping moment when you realise you can't see one of them. Of course, 99 times out of 100, they soon scamper back into view, but not this time. After a relatively calm period of observing Tudor from the middle distance, Popescu suddenly closes in on him as his attempts to find his daughter become increasingly frantic.

Popescu's film isn't about loud recriminations but the way that lives can disintegrate by degrees, Tudor's wife slowly pulling away from him, unable to stop a level of blame bubbling through - the distance between them in terms of the way they view their kids brought into sharp relief by the way they describe Maria to police officer Pricop (Constantin Dogioiu) who has been assigned to the case. In the cold space that is left, anger blooms like mold as Tudor, his beard increasingly bushy, face evermore gaunt, begins to slip into a world of his own, where obsession and alcohol hold sway. "I'm not stupid," he repeatedly Pricop, as he circles back round to the same old argument.

Much of the film relies on Dumitrache, who won a Silver Shell in San Sebastian - he is mostly captured alone, lost in his thoughts or desperately taping up 'missing posters' around the park. It's a distilled performance that gradually ratchets up the desperation as we see the four of the five stages of grief - acceptance is not on the menu - vie for control his emotions. It's his calmness that holds the threat, like a volatile substance which looks unremarkable until it explodes. Dogioiu also deserves praise for his role as Tudor's foil, his character's concerns matching our own as the dad begins to go off the deep end.

The director constantly reminds us that other people's normality is going on outside the frame of Tudor's life - in one scene in the park, an argument over a dog plays out as we watch him sitting, chatting periodically with his children or other parents, in another we see him as a child's swing moves back and forth at the front of the frame. Popescu also shows the constant reminders of Tudor's 'old' life - a child's bike against a wall, children's artwork on the wall. There is no music - not even over the credits - so that ambient sound becomes crucial, often emphasising Tudor's loneliness as the world turns on without him.

The title, for fact fans, is taken from the Tupi language for "great destructive noise" and refers to a wave phenomenon, where walls of water up to 12ft high travel up to 500 miles along the Amazon causing devastation. This may not be mentioned in the film, but it is a good analogy for the slow-build dread that Popescu generates and the destruction left behind as the credits roll.