The Monster Killer: Murder, Migration, and the Making of Modern China In the early years of the twenty-first century, a man on a bicycle moved through the farming villages of central China and killed sixty-seven people. Yang Xinhai - China's most prolific serial killer - operated across four provinces for three years while provincial police departments failed to share information, rural communities went unwarned by a state committed to the appearance of stability, and the social conditions that had produced him remained unexamined and unaddressed. The Monster Killer is not simply a true crime narrative. It is a work of historical reckoning that uses one catastrophic criminal career as a lens through which to examine the transformation of Chinese society at the turn of the millennium: the great internal migration of one hundred and fifty million people, the hukou system that made migrants legal non-persons in their own country, the labor camp apparatus that deepened criminal formation rather than interrupting it, and the institutional failures of a state that suppressed public warnings in the name of stability while sixty-seven families went to sleep unwarned. Drawing on criminology, sociology, mathematics, and the traditions of literary historical narrative, Cahir Casey asks the question that animates the best historical true crime writing: how does a human being become capable of this? The answer he finds implicates not just one man, but an entire society at its most vulnerable moment of transformation.