In the not too distant future, a very smoggy and overpopulated Earth government makes it illegal to have children for a generation. One couple, unsatisfied with their substitute robot baby, breaks the rules and gets in a lot of trouble. (Z.P.G. stands for Zero Population Growth).
When a daring mission leads a deep sea submarine team into a mysterious opening on the ocean floor, they uncover a lost underwater world and awaken its ancient race of otherworldly beings.