In medieval Cambridge, four children have been murdered. The Catholic townsfolk blame their Jewish neighbors, so to save them from the rioting mob, the Cambridge Jews are placed under the protection of the king. King Henry II is no friend of the Jews—or anyone, really—but he believes in law and order, and he desperately needs the taxes he receives from Jewish merchants. Hoping scientific investigation will catch the true killer, Henry calls on his cousin, the King of Sicily—whose subjects include the best medical experts in Europe—and asks for his finest "master of the art of death," the earliest form of medical examiner. The Italian doctor chosen for the task is a young prodigy from the University of Salerno, an expert in the science of anatomy and the art of detection. But her name is Adelia; the king has been sent a "mistress of the art of death."

In a backward and superstitious country like England, Adelia faces danger at every turn. As she examines the victims and retraces their last steps, Adelia must conceal her true identity in order to avoid accusations of witchcraft. Along the way, she’s assisted by one of the king’s tax collectors, Sir Rowley Picot, a man with a personal stake in the investigation. A former Crusader knight, Rowley may be a needed friend ... or the fiend for whom they are searching. As Adelia’s investigation takes her along Cambridge’s shadowy river paths, and behind the closed doors of its churches and nunneries, the hunt intensifies and the killer prepares to strike again...