In 1350, Cambridge is struggling to rebuild after the Black Death. Matthew Bartholomew is training new physicians to replace those who died when a friar's body is discovered inside the chest used to protect the university's most valuable documents.
The investigation leads Bartholomew and Brother Michael towards a secretive religious group meeting in a derelict church. Amid shortages of clergy, distrust of established institutions and fear that the plague may return, they uncover blackmail, deception and a campaign that uses spiritual uncertainty as cover for political and personal ambition.