'You know what it's like. Dark at teatime and sleeping indoors: nothing ever happens in the winter holidays." Or so Nancy thinks. Then the lake ices over completely and the Swallows and Amazons, along with Dick and Dorothea -- 'the D's' -- plan a race to find the North Pole. How will they reach it if they can't sail? By sledges of course! But when a blizzard blows up and there is a mix up about signals, the D's disappear into the Arctic night. Disaster looms. Can the Swallows and Amazons save their friends?