4 stars

Claustrophobia in a sleeper compartment on a long train journey has a tension all its own in this Finnish-Russian collaboration. As the frisson escalates between the two young occupants of the space, it's a compelling trip into the unknown played out in the confines of the train, with occasional forays into the Russian winter wilderness.

The journey has an intensity that may belong to that forgotten time before the smart phone, when we could lose ourselves on the internet. Compartment No 6 is set in the 1990s, so Laura (Seidi Haarla), missing the lover she has left behind in Moscow, doesn't have as those options for escape.

The film is based on a novel in 2011 by Finnish writer Rosa Liksom and directed by Juho Kuosmanen, who also co-wrote with Andris Feldmanis, working with a Finnish and Russian cast. It was a major prizewinner at Cannes last year.

The bloke Laura finds herself sharing with is babout the same age as her, but so different. The young Russian in a buzz cut, Lyoha (Yuriy Borisov), expresses himself with jerky, aggressive gestures, inflammatory language and a predatory scowl. Laura, a Finn who speaks Russian, would be happy to keep to herself but he is looking for a response.

As it happens both Lyoha and Laura are on their way to Murmansk and must put up with each other for the duration, while other passengers get on and off. There will be ample time for their little interpersonal drama to evolve, but it looks like a stand-off could erupt within a very short time. Though there are moments when Lyoha's tough guy veneer looks thin, hinting at another side to the troubled guy behaving badly.

The reasons each has for travel are in colourful contrast. Lyoha is heading to a job in a mining complex, while Laura is on her way to look at 10,000-year-old petroglyphs near the shore of the White Sea. She is a student of archaeology at Moscow University.

By way of explaining her interests to the apparent blockhead she has landed as a travel companion, Laura says that it's easier to understand the present if you understand the past. The sort of thing a someone fascinated in ancient rock carvings might say.

For his part, Lyoha is determined to make a big deal of being Russian. He has no idea what petroglyphs are, but he has a list of achievements to recite that he believes made Russia great, like defeating Nazi Germany, sending the first man into space, having more words for snow than Finnish. It would be funny were it not for the glint in his eye.

Laura holds her own pretty well against this onslaught of pre-Putin machismo, though we do wonder where things are heading on a number of occasions. Not least when she accepts a lift from Lyoha to goodness knows where during a train stopover one night. After the rudeness of a guard and a hectoring man at the public phone booth where Laura is trying to contact her lover back in Moscow, his invitation to a bed at an unknown destination seems almost welcome.

A shot of the tail lights of the car in which Laura and Lyoha disappear is repeated a number of times, a motif for the film's trip into the unknown. When the pair return to the train, with large jars of pickled vegetables, they have shed some mutual distrust, shared a joint, and even have a smile for each other.

A retreat from the brink, for a time at least. Kuosmanen is adept at keeping us guessing, at withholding information, even remaining a bit obtuse, as Compartment No 6 develops its particular rhythms.

In this semi-naturalistic journey drama, it's not just Lyoha with defences to drop. Laura has a patina of her own to leave behind. The performances of the two leads are very persuasive as their characters subtly shift before our eyes, though there are several moments when Borisov seems to have difficulty maintaining his bully-boy role.

A Finnish and Russian coproduction like Compartment No 6 is probably no longer possible now. Russia's geopolitical aggression has added another layer of significance that the filmmakers probably couldn't have foreseen while they were in production.