A post apocalyptic world in which society puritanically tries to resist the deviations
that beset their crops, livestock and people through genetic mutations.
David Strorm, never quite understanding his father's fervour for normality soon discovers that he (and certain others) deviate from the norm in a new and undetectable way. As they try to keep their difference hidden and try to be normal, they eventually discover that they won't ever fit in and with the arrival of David's sister Petra, it becomes impossible to maintain that illusion.
This story is an allegory for social change in Britian in the 1950's. It explores the tension between the social forces for change and conservatism. It also incorporates the fear of nuclear attack and genetic mutation as well as the science of genetic manipulation.
I found this to be an engaging and enjoyable read marred only slightly by a couple of plot niggles and an inevitably (unfavourable) comparison to the way Theodore Sturgeon handled a similar theme.