The very first shot of Christian Mungiu's new film, Beyond the Hills, seems to suggest one of the only concrete messages it's possible to draw from the picture: a young woman moves laboriously through a crowd of travelers alighting at a train station. They move one way, she goes the other, jostling and bumping against the tide of people before eventually reaching her destination. The shadows created by the trains lift and, as the sunlight pours into the shot, she finds and is embraced by a friend. So begins over two and a half hours of bleak, scrupulously observed drama that, astonishingly, never feels as though it's adopting a side. It presents two ways of existence - two ways of moving through life - and manages to stop at that: simply presenting them. The virtues of both are the audience's to weigh up.

The woman in the crowd is Voichita (Cosmina Stratan), and she is there to meet Alina (Cristina Flutur). Both have a shared history in a Romanian orphanage but have since parted ways, Voichita having become a nun in their native land, while Alina traveled to Germany. Immediately, an imbalance is felt between the two; affection doesn't seem to flow as easily from one side, and the tension between the women is established. They go back to the monastery, above the town and beyond the hills, introducing Alina to a place that tries its best to shut out the world, thus bringing a volatile and unpredictable sample of that world right into the bosom of the orthodox seclusion. Unease starts to grow in every heart concerned, and we settle in to watch as a remorseless criticism of the church and its ways is laid out before us.

Only, it never quite is laid out. Mungiu manages to pull off a tightrope walk of a film which somehow never puts a foot too firmly in either camp for too long, carrying a balance and poise throughout that is incredible when you reflect on what comes to pass. The inhabitants of this tiny community, although single-minded, hopelessly obedient to their priest and prone to flights of hysteria, are at the same time possessed of enormous kindness and warmth, the sincerity of which seems hard to deny. Similarly, Alina, whom we feel is going to be the character we are pushed to sympathising with, is not without flaws and impulses which we occasionally feel frustrated by. Even the priest (Valeriu Andriuta) - who, surely, will be the automatic antagonist in everyone's mind from his first appearance - has a convincing case for avoiding such a characterisation. There are indisputably black shades cast over parts of the action; stretches of time where we feel our judgement has been made and our side chosen. Yet the final scene comes and the message is literally thrown onto the screen; in reality, it's much more grey than black or white; more times than we'd like to admit, life is not simply a question of 'good' and 'bad'.

Reality is certainly what is portrayed over this slow-moving epic. The cinematography spares no detail and the landscape, while capable of beauty, is cold and unwelcoming. The two leading actresses deliver excellent performances (for which they shared the 'Best Actress' award at Cannes), full of anguish and torment - often through their eyes alone - while the cast as a whole is without fault. The only danger here is length. Such a tone, at such a running time, will undoubtedly make the piece appear laboured in the minds of many. That is a shame, yet one Mungiu will be able to live with. After such a finely traced journey through a subject almost unavoidably divisive, the fact that he is such a neutral guide is an achievement worth the work.