December 7, 1941: Five Japanese two-man mini-subs speed toward the mouth of Pearl Harbor. Four mini-subs are sunk or captured. The fate of the fifth is unknown. Late at night, nearly three quarters of a century later: Marine biologist Jack Ferrell sails into a mysterious fog off Kauai’s Na Pali coast and discovers the sunken mini-sub. But in a depression in the coral lies a greater mystery: a human skull the size of a grapefruit. Through a colleague, he learns the skull is from an extinct species of child-sized human beings who lived 12,000 years ago on the remote Indonesian island of Flores. But this skull is no fossil -- the creature it came from died recently. In search of answers, Jack joins a select team of scientists who plunge into a subterranean world deep within the rugged mountains of the mystical Na Pali coast. What should have been a routine scientific excursion becomes a deadly encounter with the unknown and a race against time as the expedition battles the elements, personal fears, and even one of their own to unearth the key to the origin of the skull and the surprising truth behind one of Hawaii’s famous legends, the Menehune.