In 1813, Napoleon wages a war of aggression in Europe, while the people of London immerse themselves in a life of profligacy. This environment concerns Swiss watchmaker William Robinson, who worries that his four sons will never develop into worthwhile human beings if they continue to live in pleasure-seeking London. Consequently, when three of his sons--Jack, a fop and a snob; Ernest, a scholarly bookworm; and Fritz, a soldier who idolizes Napoleon--return home from school for the Christmas holidays, William announces that he is moving his family to the colonies. William is unmoved by the protests of his sons and Elizabeth, his social climbing wife, and the family sets sail on a brig bound for Australia. After several non-eventful weeks, a raging storm lashes the boat, washing the crew overboard and leaving the vessel a battered hulk. When the crippled ship drifts onto a reef off the shore of an island, the family uses barrels as rafts and manages to save the livestock that was onboard the ship and reach the island. Realizing that their chances of rescue are slim because the island is not located on a trade route, the family rescues their possessions from the brig and begins to build a new life. Using the timbers from the boat, William and his sons build a house in a tree. Although the boys, including the baby Francis, begin to adapt to their surrounding, Elizabeth begs her husband to build a boat in which they can sail back to civilization. William at first refuses, but when he realizes that only their departure from the island will bring Elizabeth happiness, he agrees. The family begins to build their boat, but when a terrifying lightning storm destroys the boat and their house, William declares that it is "God's will" that they remain on the island. While chasing butterflies one day, Ernest is bitten by a poisonous spider and the family unites to save his life. He recovers and the next day, while Jack and Fritz are collecting clams on the beach, they see a ship offshore and paddle their canoe to it for help. The British crew on the ship tells the family that Europe is now at peace and Napoleon has been defeated. William declares that he intends to remain on the island, and Elizabeth decides to stay with her husband. Jack and Fritz also want to stay, but William pronounces that they have matured into men and must now marry and begin their own families. Ernest, Francis, William and Elizabeth bid farewell to Jack and Fritz, knowing that now that the island has been discovered, new settlers will soon come.