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).
TheDoctorfacestheendofhislifeastheMaster’splanshurtleoutofcontrol.Withthesoundofdrumsgrowinglouder,andanancienttrapclosingaroundtheEarth,theDoctorandWilfmustfightalone.Butsacrificesmustbemade,andthedeadlyprophecywarns:"Hewillknockfourtimes."
The relationship of a well-known journalist and a down-to-earth teacher goes through hard times when she takes a new job.