An ancient tablet scribed with inexplicable hieroglyphic-type writing found in the Grand Canyon prompts four scientists with different backgrounds and ideologies to search for a secret passage leading to the Sphinx. Their aim? To discover a ten-thousand-year-old link between Egypt and Arizona.

But once the cryptologist gleans the full import of the tablet's message, they realize that before the mystery can be solved, they must first find a cave in El Tovar Canyon.

A murder by an unscrupulous dealer in antiquities ends up complicating matters. When the U.S. government threatens to seal off the cave for reasons of national security, the scientists decide to take matters into their own hands.

What they uncover forces them to make a choice. If they reveal the secret, it could compromise the security of the United States. And if they don't, they could relegate future generations to an inhospitable world.