o’clock, when the night watch was not yet started, that is to say at the moment when the police were still all out in the garden or walking around the house, outside, and when I had left the the ground-floor perfectly free while I helped the general to bed, I felt drawn even against myself suddenly to the dining-room.  I lifted the carpet and examined the floor.  Three more nails had been drawn from the board, which lifted more easily now, and under it, I could see that the normal cavity had been made wider still!”

When she had said this, Matrena stopped, as if, overcome, she could not tell more.

“Well?” insisted Rouletabille.

“Well, I replaced things as I found them and made rapid inquiries of the police and their chief; no one had entered the ground-floor.  You understand me? — no one at all.  Neither had anyone come out from it.”

“How could anyone come out if no one had entered?”

“I wish to say,” said she with a sob, “that Natacha during this space of time had been in her chamber, in her chamber on the ground-floor.”

“You appear to be very disturbed, madame, at this recollection.  Can you tell me further, and precisely, why you are agitated?”

“You understand me, surely,” she said, shaking her head.

“If I understand you correctly, I have to understand that from the previous time you examined the floor until the time that you noted three more nails drawn out, no other person could have entered the dining-room but you and your step-daughter Natacha.”

Matrena took Rouletabille’s hand as though she had reached an important decision.

“My little friend,” moaned she, “there are things I am not able to think about and which I can no longer entertain when Natacha embraces me.  It is a mystery more frightful than all else.  Koupriane tells me that he is sure, absolutely sure, of the agents he kept here; my sole consolation, do you see, my little friend can tell you frankly, now that you have sent away those men — my sole consolation since that day has been that Koupriane is less sure of his men than I am of Natacha.”

She broke down and sobbed.

When she was calmed, she looked for Rouletabille, and could not find him.  Then she wiped her eyes, picked up her dark-lantern, and, furtively, crept to her post beside the general.

For that day these are the points in Rouletabille’s notebook: 

“Topography:  Villa surrounded by a large garden on three sides.  The fourth side gives directly onto a wooded field that stretches to the river Neva.  On this side the level of the ground is much lower, so low that the sole window opening in that wall (the window of Natacha’s sitting-room on the ground-floor) is as high from the ground as though it were on the next floor in any other part of the house.  This window is closed by iron shutters, fastened inside by a bar of iron.