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...

Escapees from a Confederate prison camp seize a balloon which is wrecked on a Pacific island, where Captain Nemo of the submarine Nautilus attempts to rescue them from the dangers of the island.