Take cover
Try to hide among the trees and wait for whatever is following you.
What happens next...
You walk along the path and as you go the fog begins to dissipate around you. You get the eerie feeling that someone is following you and as you walk you hear a second set of steps in sync with yours. The Marshy swamp bellow you seems to be clearing up as you go and you notice more trees on either side of you. In the far distance you see a castle.
Face the follower
Turn around and take an offensive stance agains whatever my be following you.
Continue
Continue along the way, you need not worry of some stranger.