A thousand years after the migration remembered in People of the Wolf, the last great glacier is melting and an enormous freshwater lake threatens the communities living around it. The Nightland People occupy ice caves near the glacier, while the Sunpath People hunt to the south and maintain a bitter rivalry with them.
The orphan Silvertip receives a vision warning that the ice will release a catastrophe, but only a weary war chief and a young girl believe him. They must overcome clan warfare and persuade both peoples to abandon ancestral homes before flood and collapsing ice destroy the world they know.