The Lives of Others (15)

So much narrative cinema pretends at the idea of redemption - the character who has an epiphany, changes his ways and, in that repulsive cliché, "moves on" - that when a convincing drama of self-transformation comes along there is a danger that we might undervalue it, or overlook it, or assume that we've seen it all before. That's because most movies can only really convey a change of mood. It's a rare picture that can persuasively dramatise a change of mind, and a change of heart. This is why you should take pains not to miss this outstanding, and astounding, German film.

The Lives of Others is the debut of a 33-year-old Cologne-born director, the extravagantly named Florian Henckel von Donnersmarck. It has already won numerous awards in its native land, a best European film accolade and this year's Academy Award for best foreign-language picture. But don't let any of that put you off. For a film so heaped with prizes and praise it is notable for a quietly spoken humility - not in its subject matter, which is ambitious and far-reaching, but in its implicit acknowledgment that heroism is at its truest when unsung and unknown. In fact, one of Von Donnersmarck's most brilliant effects is the long-delayed unveiling of where that heroism might be coming from.

Set in East Berlin during the mid-1980s, it focuses on two lives running in parallel. One is that of Gerd Wiesler (Ulrich Mühe), a captain in the GDR's state security service (the Stasi, as it was known) who commands a network of informants and breaks down suspected "enemies of socialism" by his fiendish methods of interrogation. He is one of 91,000 Stasi personnel who, backed by a further 170,000 unofficial snitches, aim to box the lives of others within a system of total surveillance. They have made a society in which spying is the natural order.

One evening, at the theatre, Wiesler's attention is drawn to the dashing figure of Georg Dreyman (Sebastian Koch), whose play has just premiered on stage. Dreyman is regarded as non-subversive by Wiesler's superior, Grubitz (Ulrich Tukur), but when a lascivious government minister, Hempf (Thomas Thieme), takes a fancy to Dreyman's vulnerable actress girlfriend Christa-Maria (Martina Gedeck), the playwright's fate is settled. Wiesler is deputed to shadow him - in other words, he is to put another's life under the state lens and wait for the spoors of guilt to manifest themselves.

Wiesler devotes himself to the job with microscopic ruthlessness. He steals into Dreyman's apartment and infests the rooms, the walls, the telephone, with bugs, then installs himself in an attic room to monitor his quarry. A stickler with a stopwatch, he seems to thrive on the very tedium of surveillance; this sinister recording angel sees nothing distasteful, or even farcical, in his noting of the playwright and his girlfriend's nocturnal silences: "Presumably have intercourse."

But by degrees we realise that Wiesler himself is a study in solitude - the loneliness of the long-distance bureaucrat - and the mischief he is paid to make unwittingly unlocks a door to his own humanity. We see it first in his pathetic attempts at befriending a call-girl, who's off to service the next Stasi agent before Wiesler has had a chance to pull up his trousers; then we find him seeking solace in a book stolen from Dreyman's apartment. It's Brecht, but hell, it's a start at least. He overhears Dreyman at the piano playing "Sonata for a Good Man", and his humourless face suddenly betrays a twitch of longing.

Mühe's minutely calibrated expressiveness is crucial here, revealing to us a working stiff thawed by compassion. With his wiretaps and his headphones, he recalls the guilt-hounded surveillance expert played by Gene Hackman in The Conversation.

Yet Wiesler's spiritual sea change is also effected by the souring of his political idealism: he comes to know about the minister's predatory womanising, and it finally dawns on him that the Party whose purity he espoused is merely a launchpad for corruption and careerism. His chance to do some good arrives after a friend of Dreyman's hangs himself; in a surge of pity and indignation, Dreyman has written an article about the high rate of suicide in the GDR and tries to smuggle it out to the Western press. A tense game of cat and mouse is entrained, wherein the search for the rogue typewriter on which the article was composed becomes an emblematic struggle between freedom and suppression.

Wiesler, officially appointed to watch his suspect, now begins to watch over him, omitting incriminating details from his reports and falsifying evidence to bamboozle his masters. In one excruciatingly taut scene he is called in for questioning by Grubitz, his boss, and their interview becomes an unspoken challenge as to who has the better poker face.

This is one of several sequences in which the layered ironies and bitter compromises of the story resonate as satisfyingly as a great novel. The climate of paranoia and suspicion in which ordinary East Germans lived is also compellingly evoked. (Good Bye Lenin! presented the comic flipside of this overview). A neighbour who has witnessed the bugging of Dreyman's apartment is warned that any attempt to warn him will result in her daughter's expulsion from university - a petty blackmail that was, one imagines, a workaday occurrence in this pinched republic of fear.

More chilling still is the scene in which Grubitz, overhearing a recruit telling his friends a Honecker joke in the refectory, forces the young man to proceed to the punchline, and then demands his name and rank. Grubitz then bursts out laughing and tells his victim that he's only joking, but years later we spot that same recruit working in the mail office steaming open the public's letters: the Stasi salt mines. I can't help thinking Milan Kundera would love that scene.

Only towards the end did I twig that Dreyman and Wiesler, intimately entwined by fate, have gone through the story without ever meeting one another. To reveal what befalls either would be unpardonable, nor must I give away the magnificence of the final scene: all that can be safely said is that it takes place in a bookshop, and features a sentence of four words that may bring a tear to your eye. To both eyes, for that matter. It pulls together, with beautiful economy, the threads of poignancy and hope which this film has so dexterously and diligently fashioned.