Farmer Maggot's Dogs

[Nerwen]

Originally Posted by Moonraker

The Nazgul sent his dog sprinting as though he was stung, so Maggot may have realised this was no ordinary trespasser. Also the Nazgul would have radiated a foul presence of fear and coldness that he would have sensed.

He did, in fact he was thoroughly creeped out by the stranger, hence his stepping up precautions. However, it seems clear from the passage in question that Maggot had no idea he was actually dealing with a supernatural being rather than just a sinister weirdo.