This movie is based around the time of the American Civil War and follows five Union prisoners of war who escape from camp by commandeering a hot air balloon and find themselves on a volcanic island in the South Pacific. The five find their survival skills tested as they try to find tools and materials to allow them to live. One of the five, Captain Cyrus Harding (Michael Craig), has the engineering skills to make bricks and build a stone house for the five to live in and a small ship. The movie charts the progress of the five, their adventures in exploring the surrounding islands, and interaction with pirates before the secret of the island is cunningly revealed.