What is the importance of Mrs. Gorley's attic in the novel, Once Upon a Dark November?

Miss Gorley's attic with its "cupboards and closets, and hiding places, nooks and crannies . . . a place where children might look to play on rainy afternoons . . . or then again, perhaps not" is a place where frightening things happen. Repeated references to stairs and banisters call attention to this place.