The Horror Nigh

Nigh's world is defined by the sewers he lives in, and is controlled by his adopted family, the Ratpeople, a group of strange beings living in a subterranean society beneath a decaying city in a ruined world. The surface fascinates him, despite the warnings he receives, and when in his wanderings he stumbles across a 'tower,' an intact building still scraping the sky though its neighbors have been reduced to ruble, Nigh is too tempted to pass it up.
From the tower he knows he will see far and wide and learn so much, just as long as he does as the beautiful Catherine and her crone of a keeper, Madame, tell him. The world will finally be his, if he stays, fully conforms... and survives.