 Leonard's secondary world is unusual in that it overlaps with the primary one and is separated from it, it seems, through nothing stronger than blind luck.Uniquely among such fantasies, Leonard never employs magic, and indeed seems at pains to explain how his underground System works.There are no women seen underground, nor any apparent means to produce food to support the Undergrounders, but rather than hoping his readers will not notice this (as the children do), he explains very concisely the why and how of this in a throwaway manner near the beginning.