Set in the Andean highlands of modern-day Peru, the book follows Paul Hemming, an American physicist and poet, as he grapples with a failing marriage and a failed career. Hemming is traveling with his wife, Sally, a successful botanist, who is working with the Peruvian government to find alternative crops to the coca grown by Peruvian farmers. Like Paul Hemming, Sally feels increasingly alienated from her spouse and she is attracted to David Cronin, an expatriate American who makes his living guiding tourists through the ruins of the Inca empire. Cronin is a mysterious man. He may or may not have links with the Sendero Luminosa guerillas, who are waging a war against the Peruvian government in the Andean highlands. Arturo Sanchez, a Peruvian military officer, keeps close watch on Cronin as he moves among the Inca ruins and he is also monitoring the movement and activities of David and Sally Hemming.