Engineer Cyrus Smith, his black servant Nab, war correspondent Gedeon Spilett, sailor Pencroff and his foster son Harbert as well as Smith's dog Top flee in a free balloon from the Richmond, which is besieged in the American civil war. However, a storm blows them into the southern Pacific, where they can save themselves on an unknown island. The fight for survival begins, supported by an unknown helper. Only late the 5 stranded are told on whose island they have landed. But time is pressing, because a volcanic eruption threatens to devour the island.