It's a measure of director Cristian Mungiu's success that this film manages to live up to and even exceed the hype that comes attached to the Palme d'Or.

The drama takes place over one day in 1987 when Otilia (Marinca) helps her university roommate Gabita (Vasiliu) seek an illegal abortion. Risking prison under Ceausescu's dictatorship, Gabita seems to be falling apart, so it's up to Otilia to facilitate the doctor and hotel room - but quite how far she's willing to go to help her friend is yet to be tested.

As the film starts the pair are making their final preparations to leave, and it quickly becomes apparent that Otilia, scared and naïve, is dependent on her stronger, more practical friend to actually make the abortion happen. Initially the dependence shows itself in small errands, as Gabita goes in search of a pack of Kent cigarettes that will be used as a bribe to oil the corrupt machinery. Her involvement grows as she makes preparations for her friend, until eventually she is asked to make a huge personal sacrifice and is then left to clean up the mess afterwards.

Playing out in what seems like real time, both Mungiu's drama and cinematography by Oleg Mutu are utterly committed to portraying the reality of the situation. Taking Otilia's point of view, the mobile camerawork and static shots combine with great discipline to give space for brilliant performances and to ratchet up the tension.

The camera is unsteady and unsettling, jogging along as Gabita strides purposefully along the street, swinging in panoramic sweeps of the crumbling tower blocks, and lingering on characters as they sit, awkwardly framed and uncomfortable in oppressive rooms.

The result is an overriding sense of the grim practicalities of living in a corrupt communist state - the strictures and constraints that come from having to constantly overcome unnecessary obstacles and struggle with the system. So when the camera comes to rest on a close-up of the aborted foetus lying bloodied on the floor, the awful reality is that this is just one more problem that Gabita must deal with and overcome on her own.

Vlad Ivanov gives a superb performance as the ironically named Mr Bebe, who agrees to perform the abortion but insists on payment in kind rather than money from the horrified girls. Arguing with them he shows the unconcerned confidence of a man who knows he has the upper hand, his temper flaring but never leading him to lose control of the situation. Once he has extracted his payment and begun to work on Otilia his informal bedside manner is repulsive, as is his insistence that he's just doing a job in return for fair payment - he has taken a huge risk so why should he settle for less than what he wants?

Part of a planned trilogy on Romania's communist years, 4 Months... doesn't talk directly about politics but shows how the constricting laws can dehumanise those living under them. What results is shocking but never asks for pity. This is a film about cruelty, but one which channels humanity. Brilliant.

It is clear that Mungiu intends the film as a comment on communism in Romania, and he has spoken about it as the first in a series of three films that will discuss the period through its urban legends, and with no direct reference to communism. As Otilia and Gabita face each other across a table at the end of their ordeal they agree never to speak about it again. Using this story and others like it as a way of exploring communism in Romania, Mungiu is just starting the discussion, and his next instalment will be eagerly awaited.