A secret, high-technology international agency called SHADO defends Earth from alien invaders.

Government officials discover a horrible plot: the Chinese are tunneling their way to the United States.

During the Vietnam War U.S. decoder Kate Meredith is plagued with guilt when her husband coerces her to pass information to him and the Viet Cong.

A former World War II pilot, now the owner of a travel agency in Hong Kong, gets involved in espionage trying to help a Chinese woman locate her son.