If Grenville knew the Indian name for Garden, he made no sign that she could read. He made no reply whatsoever, but gazed as before at the sea. He was turning at last when a low, but distinctly briefer, recurrence of the island's haunting wails arose to disturb the wondrous calm--as well as his peace of mind. There could be no doubt the tidal phenomenon was gradually but steadily failing. What might occur when it altogether ceased was more than the man could divine. He felt a vague dread of that approaching hour and of what it might develop. "It must be after midnight," he said, at last, "--time for night's ordinary dreams." Yet, when he was finally stretched on his bed, he did not lose himself in slumber. Instead he lay thinking of the island's haunting sounds and the cave somewhere underneath the headland. He had meant to attempt an inspection of this place, if only to gratify a natural curiosity. The thought occurred to him now that, in case of dire necessity, it might afford such a shelter as was not to be found on any other portion of the island. It was not a thing to be neglected. He made up his mind that the following day he would make an exploration. CHAPTER XXII A TOMB OF STONE The ladder that Grenville constructed in the morning was not entirely new. He had found upon testing the original contrivance, made for his seance with the tiger, that, although the creepers had become quite dry, they were neither weak nor brittle. He fortified the older section with additional material, however, to make absolutely certain it would not abruptly part and drop him into the sea. All morning he worked, while his smoldering fires continued to eat out the hollow for his boat, securing new length to the rungs already provided, since the distance down from the brink of the cliff was fully one hundred feet. To Elaine he explained that he thought perhaps a cave might exist in the rock. The wailing sounds, it was easy to argue, would indicate some such cavity, which he felt it important to examine. If she somewhat divined the further fact that he hoped to discover a possible retreat, should unforeseen dangers threaten, she made no revelation of her thought. It was not without considerable anxiety, however, that she finally discovered precisely what he meant to attempt. His ladder, she was certain, was far too frail for any such business as climbing down, above that boiling tide. One careless step, or a parting of the strands, and nothing on earth could save the man from death on the jutting rocks below. She had glanced at the waters under the cliff, and their crystal depths were not at all reassuring. The thorough precautions against a mishap that Grenville finally completed considerably lessened her fears, yet she had no wish to watch him descend when at length he slipped over the edge. She was gazing with fixed and wide-open eyes at the heap of rocks in which he had fastened the ladder.