The novel posits a history in which Queen Elizabeth I was assassinated just as the Spanish Armada was on its way. Protestant mobs attacked English Catholics who fought back in self-defense. With England engulfed in civil war, the Armada landed unopposed, the Spanish occupied England, suppressed Protestantism and imposed the Catholic Church as the one and only religion. Without Protestant England, Spain prevented the Protestant Netherlands from attaining independence, while the German mercantile city states that financed the Reformation were also suppressed. As a consequence, while Spanish power eventually wanes, the Roman Catholic Church has no rivals and the Pope becomes the effective secular, as well as spiritual, ruler over Europe. The Church thus also controls the restive "New World" (which approximates the United States in our timeline), as well as "Australasia", where James Cook planted the cobalt flag of the Throne of Peter, instead of the Union Flag, in the 18th century.