In 1176, King Henry the II of England persuades the physician Adelia Aguilar to accompany his daughter, Princess Joanna, on her long journey from England to marry the King of Sicily. Adelia studied medicine in Salerno, but in the disbelieving, intolerant world of Northern Europe, she must hide her skills. She masquerades as the assistant of her own eunuch assistant, the Arab Mansur. Her task is to protect and preserve the health of the princess. The King convinces her to make the journey by holding Adelia’s own infant daughter as a hostage.
The procession is troubled by a murderer, who could be trying to attack the princess or her doctor. Joanna falls ill, and Adelia diagnoses appendicitis, and then performs an operation to save her life. The question then arises whether or not her future husband will accept a bride with a surgical scar.
As in the other three novels, Adelia also uses her medical skills to solve the murders—a forensic pathologist avant la lettre.
