While working in Africa, anthropologist Julien Bonhomme encountered an astonishing phenomenon: people being accused of stealing or shrinking the genitals of strangers on the simple occasion of a handshake on the street. As he soon discovered, these accusations can have dramatic outcomes: the "sex thieves" are often targeted by large crowds and publicly lynched. Moreover, such rumors are an extremely widespread practice, having affected almost half of the African continent since the 1970s. In this book, Bonhomme examines the story of the "penis snatcher," asking larger questions about how to account for such a phenomenon unique in its spatial and temporal scale without falling prey to the cliche of Africa as an exotic other. Bonhomme argues that the public belief in sex thieves cannot be considered a superstition or form of mass hysteria. Rather, he brings to light multiple factors that explain the rumor's success and shows how the cultural dynamic can operate on a vast scale. Analyzing the rumor on both transnational and local levels, he demonstrates how it arises from the ambiguities and dangers of anonymity, and thus that it reveals an occult flipside to everyday social interaction. Altogether, this book provides both richly ethnographic and theoretical understandings of urban sociality and the dynamics of human communication in contemporary Africa and beyond.