The Mashco Piro tribe is one of the last remaining groups of people to survive only by hunting and gathering with tools that they make themselves. Residing deep in the Amazon rain forest, they are extremely isolated and have rarely been seen for nearly a century. Recently, however, they made overtures toward civilization—and killed two outsiders. In this segment, The New Yorker staff writer Jon Lee Anderson journeys up the Madre de Dios River to a remote contact point where government anthropologists are trying to establish relations with the Mashco Piro. They are charged protecting the tribe from potentially fatal contact with drug traffickers, loggers, or epidemic diseases, and with preventing further violence.