Was he a heretic or the saviour of the early modern Catholic Church? This book recounts the extraordinary life of Giovanni Morone, a pivotal figure in 16th-century European political and religious history. Morone's story is a paradoxical one. He was a papal legate at both the first failed convocation of the Council of Trent in 1542–43 and the final one in 1562–63. Hubert Jedin, the leading modern historian of the Council, credited Morone with saving it from failure. However, during the period between these two convocations, he was the subject of serious heresy accusations, leading to an inquisitorial trial that had been in preparation for years. The paradox of this illustrious diplomat, whose historical and historiographical profile oscillates between the images of both a heretic and a 'bulwark of the Catholic faith', continued until his death. This book uses Morone's story as a lens through which to examine the history of the Church and of Europe during the 16th-century religious crisis and beyond.