At dawn on a July morning, the body of a Roman Catholic priest, Duncan Aster, is found in the shallows of a lake in Cumbria, UK. His final email refers enigmatically to a woman called Susan and an Anglican priest from Ontario. The priest, Andrew Moore, turns out to be Aster's last known contact. He won't assist the police inquiry nor will he speak about the matter with his bishop.

As the battleground between Bishop Azikiwe and Reverend Moore develops, Cumbria Police decide to send an officer to Canada to observe a disciplinary hearing held in Hamilton, Ontario; a court of canon law. Sergeant Harriet Calder hopes to find out the reason for Aster's death.