"... where Williams differs from (other) writers... is in his portrayal of a world of supernatural moral law governing the interaction between two levels of states of being. For him the living and the dead exist within a single spiritual realm.
The basic premise is made clear in the second chapter of Descent into Hell. Here a London suburban estate is presented as multi-dimensional, time being contained within space, time occupying space, so that within this particular spot the present, the past, and the future are seen to be co-terminous. Whereas a similar concept can be presented materialistically (as in Alan Garner's novel Red Shift ) Charles Williams uses this concept of relativity in a theological context: the living and the dead influence each other in an eternal dimension to which both belong and of which the physical world is the sacrament. Accordingly in this particular book the moral suicide of a distinguished military historian chimes, as it were, with the physical suicide of one of the workmen who built the house in which he lives. So too the fear endured by a young woman who is subject to the visitations of a Doppelgänger is both shared with, and supportive of, the fear suffered by a sixteenth century ancestor, a victim of religious persecution. In each case the fate of an individual is related to a timeless spiritual process. Williams's vision is essentially theological.
He describes his supernatural world with extraordinary particularity. Instead of obtruding the ghostly element upon the life of everyday, he assumes that life into the supernatural dimension: it is thus impossible to banish his phantoms from our own world, because we find ourselves inhabiting theirs, and subject to its laws."
Glen Cavaliero - 'The Novels of Charles Williams'