Rick Brant and his friend Scotty are bound for the islands of the South Pacific. But beaches and the tropical climate are not what they have in mind. Deeper than divers have ever been lies the ancient temple of Alta-Yuan. Is the Spindrift's new experiment, the Submobile, capable of withstanding the pressures of the deep? If so, there may be others interested in using it for purposes other than scientific studies. Why is Captain Turk Mallane so anxious to make friends, and why does the man with the broken nose keep turning up? Things are just going too smoothly for this adventure on the high seas. Join Rick, Scotty, Hartson Brant, and Professors Gordon and Zircon as they are forced to defend themselves from a tribe of angry natives and mutineers.