A group of five Union prisoners of war—Cyrus Smith, a resourceful engineer, along with his companions Gédéon Spilett (a journalist), Pencroff (a sailor), Harbert (a young boy), and Neb (a freed slave)—escape captivity in a hot-air balloon during the American Civil War.
 
They crash-land on an uncharted island in the Pacific Ocean, which they name Lincoln Island. Using their combined knowledge, ingenuity, and natural resources, they set about surviving and thriving on this mysterious island. They face numerous challenges: wild animals, natural disasters, and unexplained phenomena.
 
Over time, they discover clues suggesting that they are not alone on the island. Eventually, they find out the island’s secret — it is connected to Captain Nemo from Verne’s earlier novel Twenty Thousand Leagues Under the Sea. Nemo has been living in hiding there with advanced technology and scientific wonders.