This book is a sequel to "Twenty Thousand Leagues Under The Sea". A

party of British adventurers, who had been ballooning, but whose trip

had ended by being cast away on a Pacific island, have various setbacks

due to both pirates and convicts who had escaped from jails in mainland

Australasia. They realise that at times there appears to be some kind

of entity that is looking after them.

This entity proves to be none other than Captain Nemo whom the reader is

expected to have met before with his submarine "Nautilus" in "20,000

Leagues". Captain Nemo has been living in a huge cave inside the very

volcanic island, where he is surrounded with immense wealth. But he is

nearing the end of his life. We are present at his end. But what

happens after that is of great interest.