Silent and dejected, they made their cautious way over the shaken roof. They walked with the greatest circumspection, to avoid falling through some new hole or freshly opened crevasse. To Stern, especially, this accident was bitter. After nearly a fortnight's exhausting toil, the miserable fiasco was maddening. "Look!" suddenly exclaimed the engineer, pointing. A vast, gaping canyon of blackness opened at their very feet--a yawning gash forty feet long and ten or twelve broad, with roughly jagged edges, leading down into unfathomed depths below. Stern gazed at it, puzzled, a moment, then peered up into the darkness above. "H-m!" said he. "One of the half-ton hands of the big clock up there has just taken a drop, that's all. One drop too much, I call it. Now if we--or our rooms--had just happened to be underneath? Some excitement, eh?" They circled the opening and approached the tower wall. Stern picked up the rough ladder, which had been shaken down from its place, and once more set it to the window through which they were to enter. But even as Beatrice put her foot on the first rung, she started with a cry. Stern felt the grip of her trembling hand on his arm. "What is it?" exclaimed he. "Look! _Look!_" Immobile with astonishment and fear, she stood pointing out and away, to westward, toward the Hudson. Stern's eyes followed her hand. He tried to cry out, but only stammered some broken, unintelligible thing. There, very far away and very small, yet clearly visible in swarms upon the inky-black expanse of waters, a hundred, a thousand little points of light were moving. CHAPTER XV PORTENTS OF WAR Stern and Beatrice stood there a few seconds at the foot of the ladder, speechless, utterly at a loss for any words to voice the turmoil of confused thoughts awakened by this inexplicable apparition. But all at once the girl, with a wordless cry, sank on her knees beside the vast looming bulk of the tower. She covered her face with both hands, and through her fingers the tears of joy began to flow. "Saved--oh, we're saved!" cried she. "There _are_ people--and they're coming for us!" Stern glanced down at her, an inscrutable expression on his face, which had grown hard and set and ugly. His lips moved, as though he were saying something to himself; but no sound escaped them. Then, quite suddenly, he laughed a mirthless laugh. To him vividly flashed back the memory of the flint spear-head and the gnawed leg-bone, cracked open so the marrow could be sucked out, all gashed with savage tooth-marks. A certain creepy sensation began to develop along his spine. He felt a prickling on the nape of his neck, as the hair stirred there. Instinctively he reached for his revolver. "So, then," he sneered at himself, "we're up against it, after all? And all my calculations about the world being swept clear, were so much punk? Well, well, this _is_ interesting! Oh, I see it coming, all right--good and plenty--and soon!"