In 1966, a group of battle-weary American GIs trekked through the Vietnamese jungle knowing each step could mean facing the enemy's guns. But instead of ambush, they stumbled upon a hidden treasure beyond their wildest dreams. It was a discovery that exacted a terrible cost.

A vacation spot picked at random, Thailand is intended to provide relaxation time for globe-trotting archaeologist Annja Creed. Yet the irresistible pull of the country's legendary Spirit Cave lures Annja and her companions deep within a network of underground chambers—nearly to their deaths. The ancient burial sites have slumbered through the ages. Yet no rest is found there—just the voices of the dead. When the dead speak, will they help Annja uncover the perplexing past of a remarkable find or will they call her to join them?