In a story by A. Blackwood, I am unable to find out the correct meaning of "screen" in the following sentence:
Of the mutinous forces that lie so thinly screened behind life, dropping from time to time their faint, wireless messages upon the soul, Field-Martin hardly discerned the existence.
In addition, how "upon the soul" can be understood? Messages that are left for the souls, or messages that are, as it were, left "on" the souls (as if written inside them)?
I would assume, from the rest of the sentence, that it could mean something like "thinly explored?"