The year is 1545, and Prince Jobst von Witz, a war weary German prince turned scholar, travels to the University of Bologna to continue his education after attending a lecture by Martin Luther. While Luther's words may have inspired Jobst to pursue further study in Italy, his association with a major figure of the Reformation raises the suspicions of the Cardinal Legato of Bologna that Prince Jobst may be Luther's spy.
Prince Jobst is asked to translate fourteen chronicles from a Norse manuscript written by Magnus of Vaksdal in 1072. The manuscript tells the brutal tale of the conversion of the pagan Greenland Norse by one Father Ulf. With the help of his mentor, Mordecai of Cordoba, Jobst completes the task, only to find that both Mordecai and the cardinal would have him create a falsely idealized version of the past where Father Ulf is characterized as a candidate for sainthood; thereby making the fourteen chronicles of The Norse Codex, a religious relic. Prince Jobst balks at creating this false history and challenges the ethics of the cardinal's request.
However, before Jobst has a chance to present his final translation, a political crisis arises in city of Bologna because of the Cardinal Legato's brutal policies. The Six Families who formally controlled Bologna's commerce before the cardinal's appointment, have conspired against him. But for the protection of Captain Oxnick, the Vatican-appointed Commander of the Swiss Guards, the cardinal would be run out of Bologna by the mercenary militias of the Six Families.
It is through Captain Oxnick that Jobst meets Lady Elena d' Urbino, a woman who reminds him of his old love Marta, burned as a witch during the Peasants' War. Elena is attracted to Jobst's knowledge of the Norse and is interested in a rare book on magic by Albertus Magnus of Cologne to which Jobst has scholarly access. Jobst is flattered and is soon under her spell. Although the cardinal's interest in The Norse Codex is put on hold, Elena and Jobst take inspiration from the love story between Magnus, a Christian, and Hulda, a pagan. Elena also longs to learn more about the "old pagan ways."
At this point The Norse Codex comprises two narratives: the story of Jobst's translation of how the two Norse lovers, the pagan Hulda, and Magnus, a Christian, fall in love and travel south toward Vinland; and the tale of how Prince Jobst and Elena fall in love as the elite Six Families of Bologna rebel against the Cardinal Legato's repressive policies. The two narrative strands are woven together, and the plot lines converge as Elena becomes more involved with Jobst. Prince Jobst finally secures Bologna from rebellion only to find that Pope Paul III has summoned the cardinal to Rome to answer charges of corruption before the highest court in the Vatican.
