The year is 2381. The place is Urban Monad 116 of the constellation Chippitts. The population of this one-thousand storey super-structure is 800,000+ and always growing. After two centuries of ruthless, selective breeding, the essence of life is to be blessworthy and to multiply; to afford one's neighbours any type of sexual fulfilment and, above all, to avoid the evil of frustration.

But, within this seemingly blissful vertical world there are individuals who feel such perverse desires as a longing for privacy, a wish to descend from the heights, to walk on earth and bask in the sunshine. These rebel throwbacks to an earlier Earth are dangerous, disruptive elements. And they must be destroyed - if they do not destroy themselves first . . .