During a perfect spring evening on Nantucket, a violent storm erupts and a dome of crawling, colored fire blankets the island. When the howling winds subside and the night skies clear, the stars appear to have shifted. The mainland has become a wilderness of unbroken forest, where tools of bronze and stone litter the beaches, and primitive natives scatter in terror.

A startling phenomenon has occurred: The island of Nantucket has been swept into the long-ago past. With its inhabitants adrift in the year 1250 BC, there is only one question to be answered: Can they survive?