Because Elidor is a novel of parallel worlds, setting is a crucial element in its structure. One afternoon, the four Watson children, tired of waiting at the Manchester station for their suburban train, decide to take a walk, choosing their destination at random. A streetfinder dial selects Thursday Street, which turns out to be an area of old Victorian buildings—some bomb damaged, some just dilapidated—which are being torn down. At the center of this desolate neighborhood stands an old church scheduled for demolition. As they enter the church one by one, the children are transported, through the intervention of a mysterious fiddler, to the land of Elidor.

Elidor is a desolate, nearly ruined medieval kingdom, a parallel world which can be entered through "thin places" in the ordinary world. The thin places are borderline areas like slums, boundary lands, and demolition sites. While it...