Former spies Malcolm and M lanie Suzanne Rannoch have fled Britain with their family to escape the exposure of Suzanne's past as a French agent in the Napoleonic Wars. The news that Malcolm's grandfather, the Duke of Strathdon, is dangerously ill makes them risk a secret voyage to Scotland in the depths of winter. But they arrive at the Rannoch castle on the Highland coast to find that all is not as expected. Dunmykel Castle holds dangerous mysteries...