Frontiers of Heresy is among the first major English-language contributions to the history of the Spanish Inquisition since Henry Charles Lea completed his classic curvey eighty years ago. Focusing on the lands beyond Castile, Professor Monter analyzes the activities of the Holy Office during an ‘Aragonese Century’ (1530–1630) when these frontier tribunals were its most active elements. This ‘other’ Spanish Inquisition virtually ignored converted Jews and their descendants, but brutally harassed Moriscos and immigrant workers from France; it executed nearly as many people for sodomy as for heresy. Despite opposition from local elites, the Inquisition performed many services for the king, sending thousands of heretics to the galleys and even capturing horse-smugglers along the Pyrenees. Frontiers of Heresy is based upon an immense variety of archival sources, and represents a significant reappraisal of one of the most important yet misunderstood institutions of early modern Europe.