In the opening scene of The Constant Gardener, British diplomat Justin Quayle (Ralph Fiennes) sees off his wife Tessa (Rachel Weisz) as she leaves on a trip from which we know she’ll never return. At a Kenyan airstrip, activist Tessa is traveling with a Red Cross physician to a meeting with an unknown purpose; within a few days, both of them will be found murdered. As Tessa heads to the plane, director Fernando Meirelles keeps the focus on Justin in the foreground, while Tessa’s shape dissolves into a blur amidst a blast of overexposed glare. That single shot of a man watching his beloved disappear from his life is, quite literally, dazzling.

So it’s perhaps even more disappointing, after such a brilliant opening, to watch the film itself dissolve into a similar blur.

It didn’t have to be like that. Meirelles--the precociously talented, Oscar-nominated director of City of God--actually makes a wise choice early on by focusing not on novelist John Le Carré’s trademark international intrigue, but on the relationship between Justin and Tessa. He flashes back to their first meeting in London--establishing a tension between Justin’s go-along-to-get-along career company man and Tessa’s fiery cage-rattler--and their impulsive decision to get married before Justin leaves for an assignment in Africa. There’s a wonderful improvisational rhythm to the interplay between Fiennes and Weisz, a natural chemistry shaped by sharp editing. For a while, this “thriller” is actually a terrific, tragic love story.

But this tale has other fish of another genre to fry. As Justin begins to probe into the events surrounding Tessa’s death, he begins to unravel suspicious dealings involving some of his government colleagues--including his boss Sir Bernard (Bill Nighy) and his best friend Sandy (Danny Huston)--and pharmaceutical companies doing business in Kenya. He’s shipped back to England, and his life is threatened. It’s quite the set-up for an emotion-packed detective story.

Only the mystery, such as it is, doesn’t take particularly long to solve. By approximately the end of the first hour, it’s fairly clear who is in bed with whom politically, as well as the specific shady activities in which the pharmaceutical company is engaged. Justin spends most of the remaining running time essentially finding additional people to tell him, “Yes, there is indeed a conspiracy.”

It’s true that in a sense, Jeffrey Caine’s screenplay adaptation uses the conspiracy as a red herring. The film is set squarely in the shadow of the current war in Iraq, and the title itself turns Justin’s hobby into a metaphor for people so buried in the minutiae of their lives that they’re unable to see what’s going on in the bigger picture. The Constant Gardener in theory becomes as much about Justin learning about himself--and the Tessa he only barely understood when she was alive--as about harsh realities of global economics.

The problem is that everything begins to feel redundant during the film’s final hour. Everything of consequence there is to know about the players in the plot, we know; everything of consequence there is to know about Justin and Tessa, we know. While Fiennes’ performance and Meirelles’ stylish direction provide some distraction, eventually the repetition of the film’s political message--building up to the trite use of mournful tribal chants and a chest-thumping speech--simply becomes wearying. It could just as easily be titled The Constant Reminders That We Exploit the Third World.

It’s inevitable in the current political climate that some people will see artistry in The Constant Gardener just because they agree with its worldview. Yet--at the risk of re-opening that can of Fahrenheit 9/11 worms--there’s a difference between a worthy idea and a great movie. After that remarkable opening, the glare of his own good intentions blinds Meirelles to a story that keeps running in circles.

THE CONSTANT GARDENER

**1/2 (two and a half stars

Starring Ralph Fiennes, Rachel Weisz, Danny Huston.

Directed by Fernando Meirelles

Rated R.