“But how?” he demanded. “Quick!”
“The tower!” I cried.
He hastened after me back to the door. I took care to lock it behind us—at least, we would be secure against surprise from that direction. Then we sped up the stair—up and up. At last, peering from one of the narrow windows, I saw we were on a level with the parapet, but there was no door—only the solid wall of stone.
Fronsac was cursing softly to himself.
“You should have let me end it down below!” he cried. “Now we shall be too late!”
“Come, there must be some way,” I muttered in perplexity. “Let us go down a flight.”
We retraced our steps, quivering with impatience. But a cry of joy burst from Fronsac as we gained the lower floor.
“There is a door!” he said.
And, sure enough, there it was—a little door of oak, set firmly in the masonry. I held the torch near it and examined it intently.
“Well, we must pause here,” I said at last, “unless, by chance, Drouet carried a key to this also. Let us see.”