The setting of Priest Island is an island to which a young man has been banished for stealing sheep, an exile which drives him into himself and finally into an acceptance of his permanent exile. A monk who lived 300 years ago on the island is the banished man's spiritual companion and counselor who offers support as he works his way through despair into acceptance. Eilean a'Chleirich or Priest Island is the most remote of the Summer Isles off Wester Ross in the Western Highlands of Scotland. Watson visited it in the company of the naturalist Frank Fraser Darling who resided there from 1937.
When Peter Costello is exiled to a deserted island for stealing sheep, Mary, a maid, decides to join him there.