Matthew Bartholomew doesn't want to travel to Peterborough in the summer of 1358, but his friendship with the lovely Julitta Holm has caused a scandal in Cambridge, so he has no choice. He is one of a party of Bishop's Commissioners, charged to discover what happened to Peterborough's abbot, who went for a ride one day and has not been seen since.

When the Commissioners arrive, they find the town in turmoil. A feisty rabble-rouser is encouraging the poor to rise up against their overlords, the abbey is at war with a powerful goldsmith and his army of mercenaries, and there are bitter rivalries between competing shrines. One shrine is dedicated to Lawrence de Oxforde, a vicious felon who was executed for his crimes, but who has been venerated after miracles started occurring at his grave.

However, it is not long before murder rears its head, and its first victim is Joan, the woman in charge of Oxforde's tomb...