As Christmas of 1354 approaches, the town is gripped by the worst blizzards in living memory. As physician of Michaelhouse, Matthew Bartholomew struggles to help the poorer citizens cope with freezing temperatures while his colleagues prepare for the festivities.

The weather has trapped many travellers in the town, including Matthew's erstwhile love, Philippa. She and her wealthy husband, Walter, are invited to Michaelhouse for the main feast, and Matthew hopes their stay will be brief - but a man found dead in a nearby church turns out to be Walter's servant. And then events conspire to ensure that Walter will never leave Cambridge again...