An old story tells of a woman who dreams every night that she is being chased, throughout a big haunted house, by a hulking monster. Night after night, the hideous thing runs after her, its breath like acid on the back of her neck...
It all seems so real...
Finally one night, the dream begins again, but this time the beast corners the poor terrified woman, and just as it's about to tear her apart, the woman finds her voice and shrieks:
"What are you! Why are you chasing me! What will you do to me!"
At that, the monster stops, straightens up, and with a puzzled expression, puts its hands on its hips and says, "How should I know? It's your dream."