Then there's that unpromising title, The Constant Gardener, which sounds more like the new Alan Titchmarsh TV series and accompanying book. Finally, the idea of Ralph Fiennes and Rachel Weisz lighting up the screen seemed very remote after their work together on Istvan Szabo's dismal dynastic saga, Sunshine, a few years back.
Well, how wrong I was, for on that last score the pairing of Fiennes and Weisz has proved a masterstroke; both of them give what might be their best-ever performances and lend this movie not just its heart but its beguiling sense of intrigue. This is nominally a thriller, yet it plays as a romance told in flashback, a posthumous reckoning of one man's love for a woman he barely knew.
It is memorably introduced by an image of leave-taking: a mild-mannered junior diplomat, Justin Quayle (Fiennes), waves goodbye to his wife, Tessa (Weisz), as she's about to board a plane. Tessa, a fiery political activist, is on a fact-finding mission in Kenyan bandit country, and takes with her a fellow aid worker, Arnold (Hubert Kounde). As they depart, the screen whites out, ominously: Justin will never see these people alive again.
The director, Fernando Meirelles, reprises this valedictory image some way into the film, and makes it resonate all over again, because by this stage we are embroiled in two slyly interwoven stories - one of a marriage, one of a murder.
Jeffrey Caine's screenplay sets up the romance between Justin and Tessa in neat, economical strokes, and moves it along so swiftly that when she asks him to take her on his latest posting to Kenya, he hardly has time to wonder if this was her plan all along. "I feel safe with you," she tells him, a tormenting irony in the light of what betides her. The back-to-front shuffle of events means that soon we are watching Justin turn up at the morgue with his friend Sandy (Danny Huston) to identify Tessa's violated corpse, and the moment Sandy retches at the sight will come back to haunt us: it transpires that he loved Tessa too, but what went on between them will only be discovered as the story unpeels its intricate layers.
The possibility that Tessa may have been unfaithful is central to the plot's ambiguity. The British High Commission decides that she was murdered in a crime of passion by her travelling companion, Arnold, and back in London Sir Bernard Pellegrin (Bill Nighy) discreetly serves up this bitter pill, along with a lunch of Dover sole, to the disconsolate widower. Disconsolate, but not duped: Justin knows that Tessa was pursuing an investigation into a dodgy pharmaceuticals company which had been testing a tuberculosis drug on certain African "guinea pigs", and finds himself driven to finish the work she started.
Having survived so long on impeccable good manners he must now emulate her "terrier" tenacity, hoodwinking passport controls to fly to Berlin and seek out a vital contact of his late wife.
This is where Fiennes's performance feels so elegantly calibrated, the slow transformation of a quiet, pen-pushing desk jockey into man of action, from a slouch into a sleuth. Having previously tended his own narrow plot - he is the "gardener" of the title - he digs deep into a stinking morass of official lies and corporate malfeasance to get to the truth, and it's the recognition of his essentially decent, self-contained nature that makes his plight so moving. (He cries only once, gazing through a window at his vanished love, and it tears at the heart.) Weisz has the more difficult role to negotiate, but she's never looked so natural, whether striding through the slums of Kenya or making a nuisance of herself at a High Commission cocktail party.
Meirelles shoots the chaos of Kenya in much the same way as he did the mean streets of Rio in his gangland debut, City of God, deploying the jittery camerawork, saturated colours and snake-quick cutting that acts like an amphetamine jolt (editor Claire Simpson does a superb job). This is a less gruelling movie than his first, yet it never shrinks from the suffering of Africa, exploited by the perfidious "aid" of the West and betrayed by its own leaders. One extraordinary shot catches shocking disparity, as the camera does a 180-degree swing from the tranquil green of a golf course to the slums of a shanty town: nothing could be so calculated to make you despair for the continent.
The Constant Gardener is an artful and absorbing effort, though for all its brilliance, it perhaps lacks an old-fashioned clout. It sometimes seems a little too high-minded to use its thriller tropes effectively. Towards the end of the movie Justin is chased in his car into the desert, and once caught, he braces himself for an assassin to emerge from the pursuing vehicle - but no, it's just an old associate from British HQ to tell him he's a marked man.
And, try as you might to couch it differently, it's basically a conspiracy-and-corruption number, the sort that "leads all the way to the top". Some clichés are too tough to weed. Yet its indignation burns white hot, and in this cynical age a little idealism can feel almost revolutionary.
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