1369. In the city of York the harvest has failed and plague has returned. Rumours spread that a spate of deaths at St Leonard’s Hospital is no accident. The hospital is in debt and has suffered theft of valuable treasures; while the appointment of a former prostitute as a lay sister provokes further outrage. Anxious to address the crisis, Sir Richard de Ravenser, Master of the Hospital, requests the services of Owen Archer, spy for his uncle John Thoresby, Archbishop of York, to investigate the deaths. Owen Archer is unwilling to become involved. There is too little to link the one to another: the riddle seems unsolvable. But careful enquiries reveal a further riddle, connected to one of the victims. Is this where the truth lies?