For fifty thousand springs, Silverhair and her kind, the last of the woolly mammoths, have lived in a remote tundra, rimmed by ice and sea and mountain. Soon to be a mother, Silverhair looks to the future with hope. But even as her life begins, the world she loves is ending. A new menace, more vicious than any enemy, is descending upon the snowlands -- a two-legged creature that kills for joy. Desperate to save their kind, Silverhair and the matriarch, Owlheart, must travel across the glacial torrents, beyond the saw-toothed mountains. There they will seek help from the distant cousins who found their destiny in the sea, and from an enemy -- an ice-faced menace known as... the Lost.