Examines the phenomenon of crypto-Judaism, how it began and how it developed. Relates the history of the Spanish Inquisition from the late 15th to the 18th centuries, in relation to its goal of rooting out and punishing Judaizers, i.e. Conversos who were charged with returning to Judaism. The accused were arrested, imprisoned, and tortured, after which most "repented" and were then punished according to the Church's rules. Approximately 40% of the Inquisition's victims were Judaizers; they were the most severely punished, often by flogging, sometimes forced to serve as galley rowers; 10% of them were killed. Inquisition archives also provide information about crypto-Jews who attempted to live double lives amidst great danger.