[2] During the Civil War, six survivors escape from a prison camp in Richmond, Virginia by gas balloon and find themselves on an uncharted island in the Pacific: leading the group is Cyrus Smith.

Far from any kind of known civilization, the island is inhabited by giant insects and animals, as well as the mad genius Captain Nemo.

After being rescued from drowning by Nemo's crewman, Smith is separated from his group, which is reduced when one of them is eaten by a giant mantis.

Meanwhile, Smith convinces Nemo to track and rescue the other survivors, unaware that pirate Captain Bob Harvey is coming to the island, looking for a lost treasure said to be hidden there.

Exploring the island, the survivors witness a stranger running through a wood and find a cave on a cliff which they make their new home.

While out collecting food, Helen encounters Blake - a pirate left behind during an earlier raid - and shelters from a storm with him.

During the subsequent fight, the survivors manage to drive off the pirates, Atherton forces Harvey into a stand-off, and Joseph is shot while departing.

As the others begin work on a new raft, Pencroff departs to try to find the treasure, needing the money to pay off his debts back in America.