At the bidding of the mysterious MacLeod's Maidens, Andrew MacKenzie and his friends (known collectively as the Stormy Petrels) are making their way on foot from Mallaig on the west coast of the Scottish Mainland, opposite Skye, south to the wild mountain wilderness that lies between Rannoch Moor and Loch Etive in Argyll. There, they are to search for a particular holly tree where the Cailleach Bheur (the supernatural Winter-Hag) hid her storm hammer long ago. If they manage to find it, they are to take it to the Gulf of Corryvreckan between the islands of Scarba and Jura and drop it down the...