I had hardly recovered from the surprise into which this new discovery had plunged me, when Rouletabille touched me on the shoulder and asked me to follow him into his room.

“What are we going to do there?”

“To think the matter over.”

I confess I was in no condition for doing much thinking, nor could I understand how Rouletabille could so control himself as to be able calmly to sit down for reflection when he must have known that Mademoiselle Stangerson was at that moment almost on the point of death. But his self-control was more than I could explain. Closing the door of his room, he motioned me to a chair and, seating himself before me, took out his pipe. We sat there for some time in silence and then I fell asleep.

When I awoke it was daylight. It was eight o’clock by my watch. Rouletabille was no longer in the room. I rose to go out when the door opened and my friend re-entered. He had evidently lost no time.

“How about Mademoiselle Stangerson?” I asked him.

“Her condition, though very alarming, is not desperate.”

“When did you leave this room?”

“Towards dawn.”

“I guess you have been hard at work?”

“Rather!”

“Have you found out anything?”

“Two sets of footprints!”

“Do they explain anything?”

“Yes.”

“Have they anything to do with the mystery of the keeper’s body?”

“Yes; the mystery is no longer a mystery. This morning, walking round the chateau, I found two distinct sets of footprints, made at the same time, last night. They were made by two persons walking side by side. I followed them from the court towards the oak grove. Larsan joined me. They were the same kind of footprints as were made at the time of the assault in The Yellow Room—one set was from clumsy boots and the other was made by neat ones, except that the big toe of one of the sets was of a different size from the one measured in The Yellow Room incident. I compared the marks with the paper patterns I had previously made.

“Still following the tracks of the prints, Larsan and I passed out of the oak grove and reached the border of the lake. There they turned off to a little path leading to the high road to Epinay where we lost the traces in the newly macadamised highway.

“We went back to the chateau and parted at the courtyard. We met again, however, in Daddy Jacques’s room to which our separate trains of thinking had led us both. We found the old servant in bed. His clothes on the chair were wet through and his boots very muddy. He certainly did not get into that state in helping us to carry the body of the keeper. It was not raining then. Then his face showed extreme fatigue and he looked at us out of terror-stricken eyes.

“On ou............