d the
gallery quitting it at a right angle, the "off-turning" gallery (winding
gallery in the plan). It was at the meeting point of the two galleries
that Rouletabille had his chamber, adjoining that of Frederic Larsan,
the door of each opening on to the "off-turning" gallery, while the
doors of Mademoiselle Stangerson's apartment opened into the "right"
gallery. (See the plan.)

Rouletabille opened the door of his room and after we had passed in,
carefully drew the bolt. I had not had time to glance round the place
in which he had been installed, when he uttered a cry of surprise and
pointed to a pair of eye-glasses on a side-table.

"What are these doing here?" he asked.

I should have been puzzled to answer him.

"I wonder," he said, "I wonder if this is what I have been searching
for. I wonder if these are the eye-glasses from the presbytery!"

He seized them eagerly, his fingers caressing the glass. Then looking at
me, with an expression of terror on his face, he murmured, "Oh!--Oh!"

He repeated the exclamation again and again, as if his thoughts had
suddenly turned his brain.

He rose and, putting his hand on my shoulder, laughed like one demented
as he said:

"Those glasses will drive me silly! Mathematically speaking the thing
is possible; but humanly speaking it is impossible--or afterwards--or
afterwards--"

Two light knocks struck the door. Rouletabille opened it. A figure
entered. I recognised the concierge, whom I had seen when she was being
taken to the pavilion for examination. I was surprised, thinking she was
still under lock and key. This woman said in a very low tone:

"In the grove of the parquet."

Rouletabille replied: "Thanks."--The woman then left. He again turned
to me, his look haggard, after having carefully refastened the door,
muttering some incomprehensible phrases.

"If the thing is mathematically possible, why should it not be
humanly!--And if it is humanly possible, the matter is simply awful." I
interrupted him in his soliloquy:

"Have they set the concierges at liberty, then?" I asked.

"Yes," he replied, "I had them liberated, I needed people I could trust.
The woman is thoroughly devoted to me, and her husband would lay down
his life for me."

"Oho!" I said, "when will he have occasion to do it?"

"This evening,--for this evening I expect the murderer."

"You expect the murderer this evening? Then you know him?"

"I shall know him; but I should be mad to affir