The two girls then took their leave, and I really felt strong hope in the success of my plan—not indeed that it was mine, for it was Harry's idea entirely, and I only gave her the instructions he had previously given me.

After this, a small packet arrived every week, sent by Sarah, through Thomas, to his father, containing seven or eight leaves of the pocket-book.

In little more than a month we had all the measurements, and were enabled to make out the entire plan, in doing which, of course our previous knowledge of the house assisted us greatly. Papa assisted me in this. I had not, at first, told him anything of what I was doing, as I wished that, in case by any chance my scheme was detected, he should be able to say that he knew nothing about it. At last, however, I was obliged to let him into the secret, and when I told him, he was very much interested and pleased; and I do not think that I should ever have succeeded in putting the parts together, and certainly have never arrived at any accurate conclusion, without his assistance.

When it was done, we found the blank space precisely where we had anticipated that we should do. It is difficult to explain the exact position, but I will endeavour to do so.

On entering the house, from the front, one found oneself in a large square hall, from one side of which the library opened, and from the other the dining-room. Opposite to the front door was an immense fireplace, in which still stood two large iron dogs, and in which in winter a great wood fire always blazed; on one side of this fireplace, the grand staircase went up, and on the other a passage led down to a room which had originally been a drawing-room, but which, from its windows being at the back of the house, had been long since turned into a kitchen; the fireplace of this room stood back to back to the one in the hall. It was in the block contained in the square formed by the backs of the kitchen and hall, the staircase and the passage, that we came to the conclusion that the secret room must be, for, even allowing for immense thickness of masonry, there was yet a large space unaccounted for. On the floor above there was also a space, directly over this, considerably larger than would have been required for the chimneys of the hall and kitchen fire, even had there been two of them—which there were not, for Sarah found that the chimney of the hall made almost a right angle, and ran into the kitchen chimney.

Papa, after going very carefully into the measurements, came to the conclusion that the room itself was situated nearly over the hall fireplace; that it might be some seven or eight feet long, by five or six wide, and that it could be little over six feet high. He thought it was approached by some short staircase opening into the hall fireplace, or into one of the bedrooms above, which abutted on the vacant space on that floor. One of these rooms had been occupied by Herbert Harmer, and the other had been, and was still, Miss Harmer's room.

Indeed papa suspected both entrances to exist, as by them, in case of necessity, provisions could be so much more readily and secretly supplied, and escape made in some disguise from the one exit, should an entrance be forcibly made at the other.

"All this is mere guesswork, my dear; but when there is so much ground to go upon as we have got, one can guess very closely indeed to the truth."

"And where should you think, papa, that the entrance is most likely to be discovered?"

"Most likely in the hall fireplace. The back and sides, if I remember right, are formed of iron, with rude ornaments upon it. The mantelpiece, too, is of old oak, and is covered with carving; undoubtedly in some of all this the secret spring is concealed. The hall is the best place to try for another reason; early in the morning, and at various times indeed, Sarah might search among all these ornaments and knobs for the spring, and if any one came suddenly into the hall, her presence there would appear only natural; whereas in either of the bedrooms, and especially that of Mr. Harmer, which is not now in use, she could hardly be often without exciting suspicion."