Chris - If I remember correctly, you often dream of black figures, and this one to me is very descriptive. The words disappearing into black, could easily be twisted into appearing from the blackness.
So your dream is looking at a ‘grey” area of your awareness. that could be disappearing or appearing - in other words on the brink. And is the face of a child - a young and immature part of you that has remained unconscious. It is an aspect of you linking you with the primitive uncluttered self not ruined by the concepts, experiences of your life - a sort of new beginning that needs to be helped to emerged from blackness.
Tony