It deals with the adventures of Bastin, Bickley, and Arbuthnot as they travel to the south sea island of Orofena.

[1][2] The story begins as the main character, Humphrey Arbuthnot—a writer of adventure stories—is married to his wife Natalie.

He gets on a yacht with two friends, Bickley, a doctor, Bastin, a minister, and Arbuthnot's dog, Tommy.

The men search a cave in the side of the volcano and find two crystal coffins with two people in them.

After being revived, Oro makes astronomical observations to confirm by stellar movements that he and his daughter have been unconscious for 250,000 years.

Yva sacrifices herself to prevent Oro's plan, thus saving millions of human beings from death.