In the 1840s, Western explorers entered the Amazon rainforest and stumbled upon the ancient ritual of head shrinking. This isolated ceremonial practice soon became an obsession to trophy collectors, setting off a bizarre international trade, and a deadly new chapter in the history of the Shuar tribe. Follow a team of anthropologists, historians, and scientists as they use DNA, forensic science, and computer modeling to examine the ancient craft of head shrinking and the story of a society of victims, who were also perpetrators.