In April 1644, two nuns fled Bologna's convent for reformed prostitutes. A perfunctory archiepiscopal investigation went nowhere, and the nuns were quickly forgotten. By June of the next year, however, an overwhelming stench drew a woman to the wine cellar of her Bolognese townhouse, reopened after a two-year absence--where to her horror she discovered the eerily intact, garroted corpses of the two missing women. Drawing on over four thousand...