Have you ever noticed that, when there are twenty or thirty people talking together in a room, there are occasional moments when everyone becomes suddenly silent, so that for a second there's a sudden, vibrating emptiness that seems to swallow up all sound? I don't know how it affects other people, but when it happens it makes me feel cold all over. Of course, the whole thing's merely caused by the laws of probability, but somehow it seems more than a mere coinciding of conversational pauses. It's almost as if everybody is listening for something - they don't know what.
Arthur C. Clarke

As the spirit wanes the form appears.