Dorothy Martin has a weakness for fine food, and when her friends Tom and Lynn inviter her to spend some time with them at a cottage on the island of Iona in the Hebrides, promising fresh crab and exquisite salmon, and since her, well, dear friend Chief Constable Alan Nesbitt is away in Brussells, she gives in and agrees to join them. The first thing that goes wrong are Tom's chest pains, keeping the Andersons in London. The second thing that troubles Dorothy are the folks traveling with her - an ecumenical group from Chicago that is anything but ecumenical. The third problem is the weather forecast. A storm is bearing down on the island, and the threat inherent in that news is enough to make even the most stouthearted think twice.
To make Dorothy's arrival even more of a horror is the fact that in her haste to leave home, she left the key to the cottage behind. The food had better be all that it was said to be; she has to spend the first night of her holiday with the bickering religious from America. Her first full day is a holy terror. The storm is building, but an opportunity to go to fabled Fingal's Cave cannot be passed up, even with the ever more cantankerous Americans along for the ride. What she wants even less is the next event: one of the group falls from the rocks in the cave and disappears beneath the waves.
It is clearly an accident, an unfortunate happenstance, and everyone is willing to accept it as such. Except for Dorothy. As the island of Iona is isolated by the storm, Dorothy begins asking questions no one wants answered, and finding answers that reveal things that she might not have wanted to know.