Had the flying presence escaped by either of these two rooms?
I knew the dining-room well.

I had had several opportunities for studying its details.

I thought I knew the library; besides, Mr.Searles had been in the library when the shape advanced upon him from the hall,--a fact eliminating that room as a possible source of approach! What then was left?
The recess which had once served as an old-time entrance.

Ah, that gave promise of something.
It projected directly toward where the adjacent walls had once held two doors, between which any sort of mischief might take place.

Say that the Misses Quinlan had retained certain keys.