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.

Mining engineer Shigeru investigates the disappearance and death of his fellow coworkers when prehistoric nymphs are discovered emerging from the mines. After an attack on the local village, Shigeru heads deeper into the mines only to make a more horrifying discovery in the form a prehistoric flying creature. Soon a second monster appears as the two converge in Fukuoka.