1360. Edward III issues a call to arms, as sporadic attacks by the French threaten to turn into a full-blown invasion. In Cambridge, fear of the enemy is magnified by the belief that foreign agents are lurking in the area. And then the first murder occurs of a French scholar living in the town. Amidst this atmosphere of swelling distrust, physician Matthew Bartholomew is called upon to investigate mysterious deaths in a nearby hospital. He quickly realises that there is something odd about the inmates and their keepers, which seems to be connected to the murders. Pressure mounts as the University and the town clamour for answers, leading Bartholomew and Michael in a frantic quest for a solution.