The book tells the adventures of five Americans on an uncharted island in the South Pacific. The story begins in the American Civil War, during the siege of Richmond, Virginia, the capital of the Confederate States of America. As famine and death ravage the city, five northern prisoners of war decide to escape in a rather unusual way – by hijacking a balloon.
The five are Cyrus Smith, a railroad engineer in the Union army, his African-American manservant Neb (short for Nebuchadnezzar), who Verne repeatedly states is not a slave but instead a loyal butler, the sailor Bonadventure Pencroff (who is referred to only by his surname, but his "christian name" is given to their boat) and his protégé Herbert (or Harbert, depending on the translation) Brown (a young boy whom Pencroff raises as his own after the death of his father, Pencroff's former captain), and the journalist Gideon Spilett. The company is completed by Cyrus' dog 'Top'[1].
After flying in stormy weather for several days, the group crash-lands on a cliff-bound, volcanic, unknown (and fictitious) island, located at 34°57′S, 150°30′W about 2,500 km east of New Zealand. They name it "Lincoln Island" in honour of American President Abraham Lincoln. With the knowledge of the brilliant engineer Smith, the five are able to sustain themselves on the island, producing fire, pottery, bricks, nitroglycerin, iron, a simple electric telegraph, a home in stone called the "Granite House", and even a sea-worthy ship. They also manage to find their geographical location.