The assassination of Prince William of Orange by a French Catholic in 1584 had immediate political consequences and a profound effect on the course of history. It was a serious setback for Protestants in the Netherlands, who were struggling for independence from the Catholic rule of the Hapsburg Empire. But the crime's ramifications were even more earth-shattering, for it heralded the arrival of a new threat to the safety of world leaders and the security of nations: a pistol that could easily be concealed on one's person and employed to lethal effect at point-blank range. In this provocative, fascinating, and enormously engaging work, noted author and historian Lisa Jardine brilliantly recounts the brazen act of religious terrorism that changed everything—and explores its long and bloody legacy, from the murder of Abraham Lincoln in 1865 to the slaying of Archduke Ferdinand in 1914, to the plague of terror and violent zealotry that infects our world today.