In 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. Tension runs ever higher as rumours and ignorance fan the flames of suspicion amid preparations for war.
And then the first murder occurs - of a French scholar living in the town.
At Michaelhouse, Brother Michael is now Master, but his reach of power in the University is under threat by the election of a new Chancellor and his cohort of dubious advisors. Soon, the Colleges begin to squabble amongst themselves, as well as with the town that never wanted a University in the first place.
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 - something dark and deadly, which seems to be connected to the growing number of murders in the town. Pressure mounts as the University and the town clamour for answers, leading Bartholomew and Michael in a frantic quest for a solution before the powder-keg of animosity in Cambridge is ignited.