Several people are killed at a hospital on Trumpington Road while university scholars are being murdered elsewhere in Cambridge. Matthew Bartholomew and Brother Michael investigate whether the two groups of deaths share a cause or merely reflect a city crowded with separate dangers.
Their suspects include royal knights, a woman accused of witchcraft, French refugees fearing retaliation during the Hundred Years' War and witnesses convinced that a ghost haunts the area. The investigators must separate political suspicion and supernatural rumour from evidence before the sanctuary offered by the hospital becomes a trap.