Island of the Burning Damned

Jeff and Frankie Callum run The Swan, an inn on the remote island of Fara, Orkney, somewhere off the English coast. Jeff, a professional novelist, hires a secretary, but this turns out to be Angela Roberts, a younger woman with whom he had an affair some time before, and who has come to the island with the intent of luring Jeff away from his wife, or at least causing trouble in their marriage. The Callums moved to Fara Island so that Jeff could escape Angela's amorous advances (although as far as Frankie knows, it was to escape the tedium of city life on the mainland).