Fifteen schoolchildren set out on a boat that was supposed to ferry them home to the New Zealand coast. The vessel loses its anchor and drifts into the open sea at night, with no sailors aboard. A violent storm the next morning prevents them from returning to the harbor, and after several days the boat grounds on a deserted island in the Pacific Ocean. Left alone for twenty months, the children must organize themselves to survive, stockpile food for the coming cold winter, and maintain hope. Three of the youngsters, Briant, Doniphan, and Gordon, step up as leaders and discover that a sailor had lived and died on the island twenty years earlier.