For a movie starring Ralph Fiennes, The Constant Gardener begins with an unusual bang. Specifically, a violent car crash, the camera flipping over and over, the shots too close to show who's involved or how it happens. Minutes later, word gets back to Justin (Fiennes) that his wife Tessa (Rachel Weisz) has been killed in the wreck. After a moment, the painfully proper Justin thanks the poor fellow who delivers the news.

Justin's story doesn't actually start with Tessa's death, but it's a pivotal moment. Directed with signature smart ferocity by Fernando Meirelles (City of God), Gardener traces Justin's shift from trusting, go-along bureaucrat to skeptical and resolute investigator. Believing that Tessa's death was brought on by her own investigation into the nefarious collusions of international drug corporations and first world governments, Justin becomes almost fierce. This transition is rooted in the movie's source, a 2001 John le Carré novel, but it hardly leads to the usual action-packing. Indeed, Justin is more melancholy than heroic, and The Constant Gardener is more meditative than thrilling.

This somber tone is only partly a function of Justin's discovering the many facets of Tessa's life that she kept hidden from him. It also has to do with the film's structure, which, like Justin, turns increasingly inward, even as it exposes broad-based corruption and indicts British officials. Justin and Tessa's unlikely but strangely convincing romance jumpstarts his internal journey. A flashback to their first meeting demonstrates their opposing temperaments and political inclinations; she challenges a lecture he's reading for an absent diplomat, specifically taking issue with its defense of the U.S. invasion of Iraq (clearly an updated addition to the novel).

At once flummoxed and smitten, Justin backtracks, insisting that he really believes her rather than his colleague, and soon enough, they're finding out all the ways that sensual, passionate, wholly pleasurable love can overcome politics. These scenes of early affection are lovely, even poetic, in particular a couple of repeated fragments: in one, they laugh and caress underneath white sheets, the light vaguely angelic; in another, she's hugely pregnant, toweling herself off after a bath, and he glimpses her through the doorway, framed on a threshold, just out of reach and absolutely at ease with her own moment. When he thanks her for "this wonderful gift" of herself, she laughs, "How very generous of me." Still, she appreciates his solidity, no matter how naïve it might be. "I feel safe with you," she tells him, granting him an identity he hadn't thought of.

Recalling her brilliant energy and blaming himself for not keeping her "safe," Justin makes himself miserable, but also pushes himself to pursue whatever "truth" he imagines to exist. He tells himself he wants to continue her work and assign proper blame to the villains, but he also wants to learn what exactly she thought was too arduous for him to bear, whether an affair with a doctor with whom she traveled, the charismatic Arnold (Hubert Koundé), or betrayals by his own supposed friends, including Sandy Woodrow (Danny Huston), acting head of the British High Commission.

Justin's adventure takes him to Kenya, where Tessa first traveled with him for his dry government business (he's a midranking career diplomat with the High Commission in Nairobi). Here the movie takes off visually, contrasting the interiors of urban, well-heeled London with vast landscapes and poverty, at once breathtaking and oppressive. Meirelles and City of God cinematographer César Charlone keep the frame a little frantic, close on faces, following and anticipating movement, intimating both the local devastation and the toll taken by Tessa and Justin's differing responses.

Tessa understands intuitively how to read her new milieu, responding with compassion, looking to save any one of the victims she might get her arms around. Justin keeps his distance, declaring that because their efforts would be futile against the tide of suffering, they can't insert themselves in the natives' lives.

Justin will learn a lesson on this score, too late to save Tessa or those she tries so desperately to help, or even to save himself. The too-lateness makes its own point, about the relentlessness of systems, be they bodily (AIDS, tuberculosis), political (Justin's co-workers), or corporate (the multinational pharmaceutical companies).

At the same time, the film falls into another familiar and rather discouraging system. Much as Tessa and Justin work as characters (thanks to subtle performances by both actors), they are troubling as bits of the larger text. They're yet another set of white figures used to dramatize, frame and make marketable a black African story. Yes, the drug companies and the government officials are bad, as are the African warlords' horseback thugs, hacking away at villagers to exact the taxes to which they feel some entitlement. But the Africans serve as context for Justin's story, fraught and anguished as it may be.

The Constant Gardener Directed by Fernando Meirelles A Focus Features release Now Playing at Ritz Bourse