Almost at the end of the tunnel, a sharklike creature darted upon them, dreadful jaws agape. With his left arm Seaton threw Margaret behind him, while with his right he swung the four-dimensional grating upon the monster of the deeps. Under the fierce power of the blow the creature became a pulpy mass, drifting inertly away upon the current, and Seaton stared after it ruefully. "That particular killing was entirely unnecessary, and I'm sorry I did it," he remarked. "Unnecessary? Why, it was going to bite me!" she cried. "Yeah, it _thought_ it was, but it would have been just like one of our own real sharks trying to bite the chilled-steel prow off of a battleship," he replied. "Here comes another one. I'm going to let him gnaw on my arm, and see how he likes it." On the monster came with a savage rush, until the dreadful, outthrust snout almost touched the man's bare, extended arm. Then the creature stopped, dead still in mid-rush, touched the arm tentatively, and darted away with a quick flirt of its powerful tail. "See, Peg, he knows we ain't good to eat. None of these hyperanimals will bother us--it's only these men with their meat hooks that we have to fight shy of. Here's the jump-off. Better we hit it easylike--I wouldn't wonder if that sandy bottom would be pretty tough going. I think maybe we'd better take to the beach as soon as we can." * * * * * From the metaled pavement of the brilliantly lighted aqueduct they stepped out upon the natural sand bottom of the open river. Above them was only the somberly sullen intensity of velvety darkness; a darkness only slightly relieved by the bluely luminous vegetation upon the river's either bank. In spite of their care they sank waist-deep into that sand, and it was only with great difficulty that they fought their way up to the much firmer footing of the nearer shore. Out upon the margin at last, they found that they could make good time, and they set out downstream at a fast but effortless pace. Mile after mile they traveled, until, suddenly, as though some universal switch had been opened, the ghostly radiance of all the vegetation of the countryside disappeared in an instant, and utter and unimaginable darkness descended as a pall. It was not the ordinary darkness of an Earthly night, nor yet the darkness of even an Earthly dark room; it was indescribably, completely, perfect darkness of the total absence of every ray of light, unknown upon Earth and unknowable to Earthly eyes. "Dick!" shrieked Margaret. "Where are you?"