Our voyage might locate the cause. But, most important of all, we hoped to locate this unknown enemy race, somewhere down there, to whose existence so much evidence had pointed. An enemy, perhaps making ready to attack our world; we must determine that, one way or the other; locate the point of attack, if attack there were to be; estimate its nature, and the best methods of repulsing it. These were the main reasons for our voyage. The fate of our world might depend upon our success--and no disappearance of a wayward son could swerve Dr. Plantet from the least detail of his starting preparations. Within an hour the affair seemed to be wiped from his mind. Flying southwest, the mailship carried us over Mexico during that evening. We passed to the Pacific at latitude twenty-two degrees N. At fifteen degrees N. and one hundred and twenty degrees W., some one thousand two hundred miles off the Mexican coast, Dr. Plantet told them that they could put us down. By local time for that longitude, it was then nearly midnight. The cranes lowered us into a placid sea; we lay awash, the three of us standing on the tiny deck of the Dolphin, watching the lights of the great liner vanish among the southwest stars. The lights winked, red and green and purple, and presently were gone. We were alone on the falling Pacific. Our enterprise was begun! * * * * * I must recount now the strange adventure to which Arturo had set himself alone. From what he afterward told Polly, and, to a lesser degree, his father and myself, I can construct a picture of it. A picture no doubt lacking much in detail, for none could fathom the emotions that beset him. Yet withal it may be fairly accurate, for I doubt if he himself could have analyzed his motives. Guiding him, no doubt, was the clear vision that upon his own slender shoulders might rest the salvation of his world. That, perhaps, was his compelling urge. I have no doubt but that he thought so. But beneath it, mingled with it, was what may have been an even stronger urge--a strange lure. He had planned it for a long time. He had fought against it, for there was a fear lurking in it, a strange instinctive dread, mingled with the urge that seemed rushing him on. He would have gone before, but he could not find opportunity. Our departure for Norfolk that morning gave him his chance. There was a night--I think it was the evening of August 1--when he made up his mind definitely that he must act alone. It was that evening we heard the newscaster say that a fast air cruiser had been dispatched by the American Government from Guam to the uninhabited island upon which the mermaid had been reported. A formidable company of marines had landed with a flourish upon the outer shoals to which the ocean now had receded. They had scrambled up to the beach and searched the island to capture this mermaid. But nothing human or otherwise had been found to capture.