The book’s subtitle, A Tale of Deadly Obsession in the Amazon, suggests the major theme of the work.

Fawcett once wrote an essay entitled “Obsession” in which he describes the “fearful torture” of “mental storms” (213). Over time, Fawcett’s obsession degenerates into paranoia, which prompts him to communicate in code and keep his intended path secret. His detailed “Case for an Expedition in the Amazon Basin,” dated April 13, 1924 and stored in the RGS archives, is marked “CONFIDENTIAL” (114). If the name “Z” had any meaning to him, he never shares it with anyone. Even in the trenches of World War I, he regales subordinates with thrilling tales of past exploits and future plans in South America. After the war, news that his rival Dr. Rice had observed ancient paintings and planned to return to the jungle “put Fawcett in a frenzy” (200). His obsession leaves his family impoverished. The two younger children, Brian and Joan, are forced to quit school. Unable to attend university, Jack trains both his body and mind in hopes of one day accompanying his father on an expedition. Fawcett cannot even afford to pay his RGS membership dues. Nina suffers patiently but most of all, as Fawcett “continue[s] to subject her to his dangerous compulsions” (116).