But his hook still prodded the empty air, while the zephyrs that played with the dangling thing seemed solely bent on his torture. The sweat oozed out on his temples, for the straining made him warm. A sense of disappointment amounting almost to despair attacked him for a moment. "I shall leap out and swim!" he told himself, at last. "I'll not remain here for the night!" He returned to the point from which Elaine had finally been heard. She did not immediately answer when he called as he had before. When her voice came down, he was certain her breath was broken. "I've--carried the last rock--over--and one or two--extra, besides." "Right ho!" responded Grenville, cheerfully. "You might stand away while I test it." He knew that a sudden throwing of his weight upon the ladder might suffice to fetch it down. He could not be sure that, with all her ready helpfulness and promptness, Elaine had so heaped the rocks above as to make the thing secure. "I can always get back here for the night," he murmured to himself, as he scanned the swirl below. "And when it calms down from that bally twist----" The whirlpool was even then subsiding, in its intermittent way. He quickly ascended the sloping ledge, the better to run and leap far outward. His pole he dropped upon the rocks as he hung there poised for his plunge. His eyes were keenly fixed on the tide. The waters became quiescent. Swiftly Grenville darted down the ledge, leaping well out, towards the end of the ladder. He was fairly in midair when his gaze was directed to a dark form loafing in the depths. Before he struck, by some quick flirt the huge form rose, coming inward, and a black fin cut through the waves. CHAPTER XXIV A DREADED VISITOR What it was that happened when he felt the waters swiftly rising all about him Grenville could never have told. He was almost certain his foot had come in contact with a heavy, pulpy surface, like a wet thing made of rubber, as he did his utmost to strike his assailant with his heel. He could only be certain that he seemed to plunge downward interminably, and that afterwards a horrible rush of waters, lashed to violence, was sounding wildly in his ears and confusing his staring eyes. Then he came to the top with a sickening conviction, that one of his legs would be gone almost before he could feel the incisions of the teeth where the shark was closing upon it. He lurched tremendously forward in the water, to close the short but vital gap between himself and the ladder. It seemed to him then a nightmare must be binding his limbs to inaction--that incredible time was elapsing while he still remained in the tide. As a matter of fact, he had moved with prodigious energy, his strokes and velocity through the water phenomenally swift. And, when he caught at the lowermost rung, he shot from the depths like some weirdly living projectile, doubled up in a knot by its speed.