An incredible discovery on the lunar farside--massive structures being erected by intelligent, living machines--could threaten the lives of the colonists living on the Moon.
And Anderson/Beason do not disappoint. Their basic approach is that mankind is on the edge of understanding nanotech, but not there yet.. and this can lead to disastrous consequences. When they are presented with alien nanotech.. and these aliens DEFINITELY know what their doing.. our ignorance and initial fumblings create a uninterrupted tension.
I'm a sucker for conclusive endings.. and this story doesn't have one... and I applaud them for it. It fits the story. You'll
enjoy the story, don't worry.