She took from her pocket a ball of thin string, one end of which was attached to a tiny brad awl.  Going into one corner of the room she fixed the brad awl into the woodwork; then, unwinding the ball, proceeded to the other end of the room, straining the string tightly, and tied a knot to mark the length.  Then she went back and crossed the room, and again make a knot to mark the width.  Then she hastily gathered up the string, pulled the brad awl from the woodwork, and put them in her pocket.  While she had been carrying this out she retained a duster in one hand, and dusted the wood work as she moved along, trusting that if Miss Penfold should look in, the string, which was of a dark color, would be unnoticed by her.  However she gave a sigh of relief when the operation was complete, and the string and brad awl hidden away.  She then continued her work until in about three-quarters of an hour Miss Penfold again appeared.

“I think that will do very well, Anna; it is quite impossible to get all the dust out of the carving.  It would take you all day to go over it, and you would need steps for the upper part.  That need only be done occasionally.”  She gave an approving glance round as she noticed that the new housemaid had carefully placed every article in the exact place in which she had found it.  Mrs. Conway gathered up the brooms and dusters and left the room, Miss Penfold carefully locking the door after her.

“That is something done,” Mrs. Conway said to herself; “and will, I think, save me an immense deal of trouble.  To-morrow I will measure the rooms next to it.  The passage runs along the side and it is hardly possible that there can be any receptacle there; the wall is not thick enough for a place of any size.  It must be at one end or the other, or else under the floor.”

The following morning she measured the dining-room, and what was now known as the housekeeper’s room, but which in years gone by had been called the still room; and the following day slipped out of doors as soon as she came downstairs and took the outside measurement of the side of the house, marking on the string the position and width of each window.  She had only now to make a plan and compare the figures.  She found that between the back of the bookcase—­for she had taken out a few books to ascertain its depth—­and the panel of the dining-room there was a thickness of two feet; but between the library and the housekeeper’s room there were fully five feet unaccounted for.

In both were deep old-fashioned fireplaces back to back; and even allowing but six inches between these, the depth there would be accounted for, but on either side of the fireplaces there would be a wide space.  There were certainly no cupboards visible in the library, for the bookcases extended from the fireplace to the wall on each side.  In the housekeeper’s room there were cupboards on each side of the chimney-piece, but these were shallow, not being above nine inches in depth; therefore behind these there was a considerable space unaccounted for.  It was evident to Mrs. Conway that her first search must lie in this direction.  Here might lie two chambers each three feet wide by eight feet long.