Bologna, 1858. The Pope still rules like a monarch in much of Italy. After dark, officers of the Inquisition knock at the door of the Jewish merchant Mamolo Mortara and seize his six-year-old son. Edgardo, they report, has been secretly baptised and, as a Christian child, may no longer live in a Jewish household. He is whisked away to Rome to be brought up a Catholic. The household's illiterate Christian servant claims to have baptised the boy as a baby, fearing he might die of some childhood illness and miss out on a Catholic heaven. The story has reached the ears of the Inquisitor of Bologna, Father Pier Gaetano Feletti, and ultimately of the Pope, Pius IX - who has sanctioned the kidnapping. The story of how the Mortara family fight to win their son back for themselves and for Judaism makes heart-rending but riveting reading. This is not a novel, although, despite its analytical and sober prose, it often reads with the intensity of a thriller. The story of Edgardo Mortara is a carefully documented non-fictional account by a noted social historian. David Kertzer argues that the case was one of the major catalysts, both for the unification of Italy and the end of papal rule. The Pope and his Inquisitor were only doing what the church had done in many similar cases over previous centuries. But the case became such a cause celebre with liberal, modernising opinion in the ferment of mid-19th Century Europe, that it unleashed forces the still medievally-minded papacy was unable to control. The unprecedented publicity the case aroused in Protestant Britain and America had less effect on Pius IX than the geopolitical consequences of offending Catholic nations closer to home. Already at the mercy of Europe's two rival Catholic empires, France and Austria, and dependent on their support for his continuing rule, the Pope was irreparably weakened by France's disgust with his 'unnatural' attack on the sanctity of the family. While conservative Austria remained loyal (and happy to keep its troops in the papal lands of Northern Italy), France and the expansionist Kingdom of Sardinia seized on the Mortara case as ammunition against papal authority while Garibaldi's nationalists marched on Rome itself. But although Pius lost the war, he won the battle for Edgardo's soul, adopting the boy as a son and eventually seeing him ordained as a priest who made it his mission to win souls for Christianity. Jews also won a victory of sorts. The Mortara affair was a new departure in Jewish history, according to Kertzer, because 'after centuries in which such events happened regularly, the larger world finally took an interest, finally rose in protest'. It also helped to catalyse the creation of national and international Jewish defence organisations in Europe and the United States. Yet the case is barely discussed in mainstream Italian history, Kertzer argues, because it is an embarrassment both to the Church and to Italy's Jews. It highlights the fact that until recent times the Church rejected religious toleration and operated an Inquisition, and shows that its 'transition from medieval fundamentalism to modernity took place only in the present century' - to say nothing of the influence of official Catholic anti-semitism on the thinking of Italian and German fascism. To the Jews, meanwhile, the affair demonstrated the community's vulnerability to the political power of the Church. Kertzer sheds light not only on an historical event but on the ghettos and relations between masters and servants, Jews and Christians that a straight social history would not have revealed. Kertzer has a personal interest: his father was a Jewish chaplain who conducted the first Sabbath service in Rome after World War II with the city's chief Rabbi, Israel Zolli, in the synagogue. Six months later, he rose to Zolli's defence when Zolli converted to Catholicism. It is testimony to Kertzer's skill as a writer as much as his honesty as an historian that his account is such a gripping read. The Kidnapping of Edgardo Mortara by David I Kertzer Vintage, $150