The two-page preface finds Grann in the Xingu River region of the Amazon jungle, holding a map that features the letter Z in the middle, and explaining to the reader why he is there—or at least why he has convinced himself he is there. Grann had conducted extensive research into the decades-long quest for the lost City of Z, an ancient civilization purportedly hidden deep in the jungle. In the early 20th century, notwithstanding the environmental-determinist argument that the inhospitable jungle could not have sustained a complex ancient civilization, some explorers became obsessed with finding the city. Grann hints that a similar kind of obsession now drives him deeper into the Amazon.

Chapter 1 opens in January 1925. Percy Harrison Fawcett, a famed British explorer, is set to depart from Hoboken, NJ, and embark upon another journey into the Amazon. This time, he is searching for the lost City of Z. In nearly two decades of exploration, Fawcett has accumulated evidence pointing to the existence of an ancient civilization in that region. Now, having secured funding from American and British sources, he hopes to make the discovery of the century.