"Cinchona revolutionized the art of medicine as profoundly as gunpowder had the art of war." -- Bernardino Ramazzini, Physician to the Duke of Modena, Opera omnia, medica, et physica, 1716 In the summer of 1623, ten cardinals and hundreds of their attendants died in Rome while electing a new pope. The Roman marsh fever that felled them was the scourge of the Mediterranean, northern Europe and even America. Malaria, now known as a disease of the tropics, badly weakened the Roman Empire. It killed thousands of British troops fighting Napoleon in 1809 and many soldiers on both sides of the American Civil War. It turned back travelers exploring West Africa in the nineteenth century and brought the building of the Panama Canal to a standstill. Even today, malaria kills someone every thirty seconds. For more than one thousand years, there was no cure for it. Pope Urban VIII, elected during the malarial summer of 1623, was determined that a cure should be found. He encouraged Jesuit priests establishing new missions in Asia and in South America to learn everything they could from the peoples they encountered. In Peru a young apothecarist named Agostino Salumbrino established an extensive network of pharmacies that kept the Jesuit missions in South America and Europe supplied with medicines. In 1631 Salumbrino dispatched a new miracle to Rome. The cure was quinine, an alkaloid made of the bitter red bark of the cinchona tree. Europe's Protestants, among them Oliver Cromwell, who suffered badly from malaria, feared that the new cure was nothing but a Popish poison. More than any previous medicine, though, quinine forced physicians to change their ideas about illness. Before long, it would change the face of Western medicine. Yet how was it that priests in the early seventeenth century–who did not know what malaria was or how it was transmitted–discovered that the bark of a tree that grew in the foothills of the Andes could cure a disease that occurred only on the other side of the ocean? Using fresh research from the Vatican and the Indian archives in Seville, as well as documents she discovered in Peru, award-winning author Fiammetta Rocco chronicles the ravages of the disease; the quest of the three Englishmen who smuggled cinchona seeds out of South America; the way in which quinine opened the door to Western imperial adventure in Asia, Africa and beyond; and how, even today, quinine grown in the eastern Congo still saves the lives of so many suffering from malaria.