The team from NWIDI is at it again! This time, a trip to southern Japan to investigate the mysterious underwater pyramid off the coast of Yonaguni Island involves the four friends in a case of murder and international kidnapping.

The maiden flight of the team's newly acquired Learjet begins with a dramatic landing in the Aleutian Islands of Alaska and, after a run-in with Department of Justice agents in Tokyo, leaves the team thinking they should never have left home. When they finally touch down on Yonaguni, a Japanese-American exchange student introduces them to know the small island of 1,200 people - and the dark secret being protected there.

Further investigation leads the team to a startling discovery about the true nature of the island and its original inhabitants.