I stepped within and, striking a match perceived that I was standing inside a vast cave—­a vaulted chamber that ran apparently straight into the heart of the mountains.

Great stalactites hung from the roof and dripped water upon the floor, on which numerous small stalagmites were forming, where they had not been crumbled away by the passage and repassage of sleighs.  These had left two well-defined tracks in the soft stone under my feet.

The cave was one of those common formations in limestone hills.  How far it ran I could not know, but I had little doubt that at last I was well upon my approach to the chateau.

The interior was completely dark.  At intervals I struck matches from the box which I had brought with me, but the road always ran clear and straight ahead, and I could even guide myself by the ruts in the ground.

And every time I struck a match I could see the vaulted cavern, wide as a great cathedral, extending right and left and in front of me.

I must have been journeying for half an hour when I perceived a faint light ahead of me, and at the same time I heard the gurgling of a torrent somewhere near at hand.

The light grew stronger.  I could see now that the cavern had narrowed considerably:  there were no longer any ruts in the ground, and by stretching out my arms I could touch the wall on either side of me.  I advanced cautiously until the light grew quite bright; I saw the tunnel end in front of me, and emerged into an open space in the heart of the hills.

I say an open space, for it was as large as two city blocks; but it was as though it had been dug out of the mountains by an enormous cheese scoop, for on all sides sheer, vertical walls of rock ascended, so high that the light of day filtered down only dimly.  A swift river, issuing from the base of one of these stupendous cliffs, ran across the opening and disappeared into a cave upon the other side.

I glanced at my watch.  It seemed that I had been travelling for an interminable time, but it was barely eleven o’clock.  I sat down to eat, and the thought occurred to me that this would make a good camping place, if necessary, for it was quite warm at such a depth below the surface of the hills, and my fur coat had begun to feel oppressive.  I felt drowsy, too, and somehow, before I was aware of any fatigue, I was asleep.

That was a lucky thing, for I was not destined to sleep much the following night.  It was three o’clock when I awoke, and at first, as always since my journey began, I could not remember where I was.  And, as always, it was the thought of Jacqueline that recalled to me my surroundings.

I sprang to my feet and made hasty preparations to resume my journey.

A short investigation showed me that I had come into a cul-de-sac, for there was no path through the opposite hills.  There were, however, a number of extensive caves in the porous limestone cliffs, any of which might prove to be the sequence of the road.