December 7, 1941, Pearl Harbor: Five Japanese two-man mini-subs speed toward the mouth of the harbor. Four mini-subs are sunk or captured. The fate of the fifth sub, I-16, is unknown.

Late at night, nearly three quarters of a century later: Marine biologist Jack Ferrell sails into a mysterious fog off of Kauai's Na Pali coast.

Dense fog banks don't form in Hawaii . . . or so he thought. They certainly don't glow in the dark.

Concealed within the mist is the sloop Julie Ann floundering in a rogue remnant of drift net. A young woman's scream pierces the damp air, and he rushes to her rescue.

The next morning, Jack dives to check the damage done to the reef by the net and discovers a sunken WWII Japanese mini-sub and the answer to a Pearl Harbor enigma: the fate of I-16. 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 being that lived 12,000 years ago on the remote Indonesian island of Flores. But this skull is no 12,000-year-old fossil.

In search of answers, Jack, the woman from the Julie Ann, two close friends, and a select team of scientists plunge into a subterranean world deep within the rugged mountains of the mystical Na Pali coast. And what should have been a routine scientific excursion becomes a deadly encounter with the unknown and a race against time when 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.