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 our first questioning him he told us that he had gone to bed immediately after the doctor had arrived. On pressing him, however, for it was evident to us he was not speaking the truth, he confessed that he had been away from the chateau. He explained his absence by saying that he had a headache and went out into the fresh air, but had gone no further than the oak grove. When we then described to him the whole route he had followed, he sat up in bed trembling.

“‘And you were not alone!’ cried Larsan.

“‘Did you see it then?’ gasped Daddy Jacques.

“‘What?’ I asked.

“‘The phantom—the black phantom!’

“Then he told us that for several nights he had seen what he kept calling the black phantom. It came into the park at the stroke of midnight and glided stealthily through the trees; it appeared to him to pass through the trunks of the trees. Twice he had seen it from his window, by the light of the moon and had risen and followed the strange apparition. The night before last he had almost overtaken it; but it had vanished at the corner of the donjon. Last night, however, he had not left the chateau, his mind being disturbed by a presentiment that some new crime would be attempted. Suddenly he saw the black phantom rush out from somewhere in the middle of the court. He followed it to the lake and to the high road to Epinay, where the phantom suddenly disappeared.

“‘Did you see his face?’ demanded Larsan.

“‘No!—I saw nothing but black veils.’

“‘Did you go out after what passed on the gallery?’

“‘I could not!—I was terrified.’

“‘Daddy Jacques,’ I said, in a threatening voice, ‘you did not follow it; you and the phantom walked to Epinay together—arm in arm!’

“‘No!’ he cried, turning his eyes away, ‘I did not. It came on to pour, and—I turned back. I don’t know what became of the black phantom.”

“We left him, and when we were outside I turned to Larsan, looking him full in the face, and put my question suddenly to take him off his guard:

“‘An accomplice?’

“‘How can I tell?’ he replied, shrugging his shoulders. ‘You can’t be sure of anything in a case like this. Twenty-four hours ago I would have sworn that there was no accomplice!’ He left me saying he was off to Epinay.”

“Well, what do you make of it?” I asked Rouletabille, after he had ended his recital. “Personally I am utterly in the dark. I can’t make anything out of it. What do you gather?”

“Everything! Everything!” he exclaimed. “But,” he said abruptly, “let’s find out more about Mademoiselle Stangerson.”