The girl waited. She was sorely troubled, surprised, even humiliated at being the witness of this extraordinary and varied display of emotion. She felt a sense of intrusion that was almost unjustifiable, even in a detective. What right had anyone to spy upon a communion between God and man?
He rose, at length, rose and walked uncertainly forward, stumbling among the ragged rocks. He made for the far hillside that was cluttered with huge fragments of stone, some weighing many tons and all tumbled helter-skelter as if aimlessly tossed there by some giant hand. And when he reached the place he threaded his way between several great boulders and suddenly disappeared.
Josie hesitated a moment what to do, yet instinct urged her to follow. She had a feeling that she was on the verge of an important discovery, that events were about to happen which had been wholly unforeseen even by old Cragg himself.
She was taking a serious risk by venturing on the stony ground, for under the moonlight her dark form would show distinctly against the dull gray of the stones. Yet she climbed the fence and with her eye fixed on the cluster of rocks where Old Swallowtail had disappeared she made her way as best she could toward the place. Should the old man reappear or the owner of the strange automobile emerge from the rocks Josie was sure to be discovered, and there was no telling what penalty she might be obliged to pay for spying. It was a dreary, deserted place; more than one grave might be made there without much chance of detection.
In a few minutes she had reached the hillside and was among the great boulders. She passed between the same ones where Mr. Cragg had disappeared but found so many set here and there that to follow his trail was impossible unless chance led her aright.
There were no paths, for a rubble of small stones covered the ground everywhere. Between some of the huge rocks the passage was so narrow she could scarcely squeeze through; between others there was ample space for two people to walk abreast. The girl paused frequently to listen, taking care the while to make no sound herself, but an intense silence pervaded the place.
After wandering here and there for a time without result she had started to return to the entrance of this labyrinth when her ears for the first time caught a sound—a peculiar grinding, thumping sound that came from beneath her feet seemingly, and was of so unusual a character that she was puzzled to explain its cause.
The shadows cast by the towering rocks rendered this place quite dark, so Josie crouched in the deepest shade she could find and listened carefully to the strange sound, trying to determine its origin. It was surely under ground—a little to the right of her—perhaps beneath the hillside, which slanted abruptly from this spot. She decided there must be some secret passage that led to a cave under the hill. Such a cave might be either natural or artificial; in either case she was sure old Cragg used it as a rendezvous or workshop and visited it stealthily on his "wakeful" nights.
Having located the place to the best of her ability Josie began to consider what caused that regular, thumping noise, which still continued without intermission.
"I think it must be some sort of an engine," she reflected; "a stamp for ore, or something of that sort. Still, it isn't likely there is any steam or electrical power to operate the motor of so big a machine. It might be a die stamp, though, operated by foot power, or—this is most likely—a foot-power printing-press. Well, if a die stamp or a printing press, I believe the mystery of Old Swallowtail's 'business' is readily explained."