Mild-mannered Marina Singh is sent by a drug company to Brazil to find her onetime mentor, the imperious Dr. Annick Swenson, who hasn't been heard from in two years. Swenson is deep in the Amazon, studying women of an obscure tribe who can bear children into their 60s and 70s. But Swenson has gone off the rails, and Singh has to play Marlow to her Kurtz in a Heart of Darkness for the pharmaceutical era. 6/7