As early as 1929 slight cataclysms had begun to tear up the sea-floor of this region, and of late--1935--seismographs and cable companies had reported titanic upheavals and sinkings of the ocean bed, changing hundreds of miles of underwater territory. Finally Washington decided to chart the alterations this series of sub-sea earthquakes had wrought. And for this job the _NX-1_ was detailed. A super-submarine fresh from the yards, small, but modern to the last degree, she contained such exclusive features as a sheathing of the tough new glycosteel, automatic air rectifiers, a location chart for showing positions of nearby submarines, the newly developed Edsel electric motors, and automatic teleview screen. When below surface she was a sealed tube of metal one hundred feet long, and possessed of an enormous cruising radius. From the flower of the Navy some thirty men were picked, and in company with the mother-ship _Falcon_ she put out to combine an exhaustive trial trip with the practical charting of the newly changed ocean floor. Now this work was almost over. Keith Wells told himself that he, like Bowman, would be glad to set foot on land again. This surveying was important, of course, but too dry for him--no action. He smiled at the lines of boredom on Hemmy's brow as the younger man stared gloomily into the teleview screen. And then the smile left his lips. The radio operator, in a cubby adjoining the control room, had spoken into the communication tube: "Urgent call for you, sir! From Captain Knapp!" * * * * * Wells reached out and clipped a pair of extension phones over his ears. The deep voice of Robert Knapp, captain of the mother-ship _Falcon_, came ringing in. It was strained with an excitement unusual to him. "Wells? Knapp speaking. Something damned funny's just happened near here. You know the fishing fleet that was near us yesterday morning?" "Yes?" "Well, the whole thing's gone down! Destroyed, absolutely! The sea's been like glass, the weather perfect--yet from the wreckage, what there is of it, you'd think a typhoon had struck! I can't begin to explain it. No survivors, either, so far, though we're hunting for them." "You say the boats are completely destroyed?" "Smashed like driftwood. I tell you it's preposterous--and yet it's the fact. I think you'd better return at once, old man; you're only half an hour off. And come on the surface; it's getting light now, and you might pick up something. God knows what this means, Keith, but it's up to us to find out. It's--it's got me...." His tones were oddly disturbed--almost scared--and this from a man who didn't know what fear was. "But Bob," Keith asked, "how did you--" "Stand by a minute! The lookout reports survivors!" * * * * *