IN A remote area of northern Kenya, the region's most dedicated activist, the brilliant and passionate Tessa Quayle (Rachel Weisz), has been found brutally murdered.

Tessa's travelling companion, a local doctor, appears to have fled the scene, and the evidence points to a crime of passion.

Sandy Woodrow (Danny Huston), Sir Bernard Pellegrin (Bill Nighy), and the other members of the British High Commission assume that Tessa's widower, their mild-mannered and unambitious colleague Justin Quayle (Ralph Fiennes), will leave the matter to their discretion. They could not be more wrong This career diplomat's equilibrium has been exploded by the loss of the woman he was deeply devoted to. They were opposites whose attraction sustained a marriage, the memories of which now spur Justin to take decisive action for the first time in his life and diplomatic career.

Haunted by remorse and jarred by rumours of his wife's infidelities, Justin surprises himself by plunging headlong into a dangerous odyssey. Determined to clear his wife's name and "finish what she started," Justin embarks on a crash course to learn about the pharmaceutical industry, whose crimes Tessa was on the verge of uncovering, and journeys across two continents in search of the truth.

His eyes are soon opened to a vast conspiracy at once deadly and commonplace, one that has claimed innocent lives and is about to put his own at risk.

Director Fernando Meirelles states: "The chance to take on some of the pharmaceutical industry was only one of three elements that made me want to direct The Constant Gardener.

"Another was the chance the choice to shoot in Kenya. And it is also and fundamentally a very original love story; a man who marries a younger woman, and it's after she dies that he truly falls in love with her and goes looking for her. It's a beautiful tale, with a touch of the existential to it."

"For me, theirs is a retrospective love affair,'" concurs Ralph Fiennes, who plays the title role.

"There are two equal parts to this movie. On the one hand, it's a political thriller about corporate wrongdoing, malfeasance and manipulation. On the other, it's about the relationship between Justin and Tessa Quayle.

"Justin's journey traces not only what Tessa was investigating; he's also playing detective about their relationship. This man rediscovers and re-assesses his own relationship with his wife. It's a wonderful part, because he goes from being a reticent nice guy to being someone who is forced to confront some pretty tough truths about the world. I hope that the audience sees him as a kind of Everyman."

Rachel Weisz, who takes the pivotal role of slain activist Tessa Abbott Quayle, adds: "The love story and the political thriller element are completely interlocked one doesn't happen without the other, and that's the cleverness of both John le Carr's novel and Jeffrey Caine's adaptation. Because of Justin's love for Tessa, he goes on a journey of discovery where he reaches a new level of self-knowledge, but he also discovers a huge political scandal."

Referring to the company at the centre of the investigation, Ralph Fiennes states: "There are huge questions about Big Pharma. Fernando gave me some background material, including Dying for Drugs. The companies are not obliged to disclose a lot of information about how they test or make their drugs.

"There's big, big money involved in the development, patenting, and marketing of a new drug; there's no question that the pharmaceutical industry has one of the most powerful lobbies in the United States. I'm sure there are companies out there wanting to produce good, effective drugs at reasonable prices but a lot of people want and need to ask tough questions of the industry as a whole."

Rachel Weisz agrees, noting: "It's David and Goliath; the little people taking on the great big corporations. I believe that pharmaceuticals are second only to oil now; it is a massive business. They make all this money, yet people in developing countries can't afford the drugs that could save their lives."