A scientist named Marina Singh receives word that her office partner has died while visiting the company’s research lab somewhere in Brazil. The tragedy of that news is compounded by the curt letter that announces his death. On a blue aerogramme now two weeks old, the lab director has written: “Given our location, this rain, the petty bureaucracies of government (both this one and your own), and the time sensitive nature of our project, we chose to bury him here.” Eager — possibly too eager — to retrieve the body and discover what progress the lab is making toward development of a revolutionary fertility drug, the company chairman prevails upon Marina to fly to Brazil and investigate.

That journey “to the beating heart of nowhere” takes up more than half the novel, but it’s time Patchett uses to explore Marina’s past and her anxiety about confronting Dr. Swenson, the caustic director of the jungle laboratory. This is, among several other fascinating themes, a story about mentors and how they keep us in thrall long after we seem to have taken control of our lives. Marina hopes she doesn’t remember, but the older woman was her supervising physician years ago in Baltimore when their careers intersected one tragic night.

Although the director is no Mr. Kurtz, Swenson is “the uncontested kingpin” who greets Marina after an arduous journey into the jungle by saying flatly, “You shouldn’t have come.” Like John le Carre’s “The Constant Gardener,” “State of Wonder” explores the unsavory behavior of Western pharmaceutical firms in Third World countries, but Patchett’s microscope is more finely calibrated to observe the strange choices individuals make in the remote wilderness of their own conscience.

The result is less an expose of a vast corporate conspiracy than a revelation of human nature. Removed from the inconvenience of financial, legal and ethical oversight, Swenson has spent years pursuing her own medical vision, and she confronts Marina with both the power of her authority and the logic of her private morality. Is the famous doctor exploiting primitive people for her employer or protecting them? And in any case, will the chaotic fecundity of nature prevail over any efforts to tame it in a petri dish?

Swenson grows more fascinating with each development in a story pregnant with surprises and reversals. She treats Marina with startling condescension, thwarting all her efforts to discover what really happened to her dead office mate or how their medical work is progressing. “No one tells the truth to people they don’t actually know, and if they do it is a horrible trait,” Swenson says bitterly. “Everyone wants something smaller, something neater than the truth.”