After laboring for thousands of years, the people of Earth, fleeing ecological disaster, have built a new, clean, stable world on a worldwide platform erected over the entire land surface of the Earth. Everything is going well--except for Carl Magner, the man who's been having bad dreams. He shouldn't be having dreams at all, because dreams have been banished from the society of the Euchronian Millennium, but somehow he is, and his dreams are showing him the "Underworld." The real surface of the Earth, the Underworld that the Euchronian Millennium has left behind, still maintains life, human and otherwise, life that's adapted to a world without sky or sun, still evolving in response to extreme environmental challenges. Dreams are only dreams, but they're a provocation nevertheless, not merely for Carl Magner, but for the whole of Euchronian society. Can Heaven be truly Heaven, if Hell still festers in its entrails?