The legendary empire of the lost continent of Mu reappears to threaten the world with domination. While countries unite to resist, an isolated World War II Captain has created the greatest warship ever seen, and possibly the surface world's only defense.

When the Earth's polar ice caps begin melting at a terrifying pace, the United Nations sends an expeditionary force to investigate... one that is completely destroyed by the vanguard of an invasion from beneath the Earth! As the whole planet watches in horror, the U.N.'s naval armada is crushed beneath the invaders' giant gravitonic rings! The nations of the world are helpless, but even as the enemy's giant cylinders encircle the globe, a secret organization of men and women being to mobilize a last ditch defense, a secret weapon built for, but never used in, World War II. After fifty years in hiding, the ultimate attack sub is finally going to get its baptism by fire... with the fate of all mankind hanging in the balance!