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 group of scientists developing an engine for interstellar travel see their funding cut after a fatal disaster, the disgraced group must resort to criminal activity to finance their operation as they rebuild their space time device.