"It sounds preposterous," Knapp murmured, shaking his head. "Octopi, you say--and clad in metal suits! Running a submarine more powerful than the _NX-1_! Armed with a ray--a paralyzing ray! I can't believe--I can't conceive--"

"You've seen the men!... Knapp, if I were you I'd swing my eight-inchers out, bring up the plane catapult and keep the deck torpedo tubes loaded and ready. It's best to be prepared; G.o.d knows what's going on underseas these days!"

First Officer Graham appeared at the door. "Work finished, sir," he said. "Ready to cast off."

"Thank heaven!" Wells muttered, and stretched out his hand to Robert Knapp. "Broadcast what I've told you, Bob, and say that the _NX-1_ won't be back till everything's under control. I'll keep in touch with you. So long!" And he was gone before the captain could even wish him good luck.

Orders raced from her commander's fingers on the stud board in the control room. "Crash Dive" filled her tanks and put her nose perilously down, so that in thirty seconds only a swirling patch of water was left to show where once she'd lain. A brief command to the helmsman and she pointed straight for the dark cavern marked on the chart.

When well under way, Keith descended with Graham to inspect the new torpedo firing system, and found it in good working order. "Graham,"

he ordered tersely, "instruct the crew fully about rushing to the control room on one ring of the general alarm. And send the cook up to me in a minute or so. I'll be in Sparks' cubby."

Above again, he instructed the radio man to rig a remote control sender and receiver in the insulated control room. The need for centering the whole crew there during engagements would crowd the room awkwardly, but at other times, while proceeding on their inspection of the cavern lair, they could remain at their regular posts.

That, at least, was Wells' plan.

He looked up and found the cook, McKegnie, grinning at him from the door of the control room. Keith smiled, running his eyes over the portly magnificence of his gently perspiring figure. "Keg," he said cheerfully, "I want you to move your hot plate and culinary apparatus up here; you see, we're all likely to be crowded in here for some time, and your coffee's going to be an absolute necessity." He couldn't resist a crack at McKegnie's well-known and pa.s.sionate curiosity as to what made the thigmajigs of the control board work: "And besides, it'll give you a chance to observe the instruments and perfect yourself for your future career as a naval officer. Much better than a correspondence course in 'How to Be a Submarine Commander,' eh?"

Cook McKegnie grinned sheepishly, and left. He was well used to such jests, but he never would admit that his extraordinary interest in watching the ship's wheels go round was accompanied by a miraculous inability to comprehend why they went round....

Fifteen minutes later the helmsman's cry, "Cavern showing, sir!" swung the commander to the teleview screen. The dark, kelp-shrouded opening he knew so well was already looming on it. And he was prepared.

"Enter," he said, while his punched studs ordered, "Quarter Speed, Ready at Posts, Tanks in Trim." The _NX-1_ slackened her gait, balanced cautiously, and struck a straight, even course as she crept closer to the cleft entrance through which, some two hours earlier, the octopi ship had nosed.

Screws turning slowly, she edged through the jagged cavern. Shades of inky blackness grew on the teleview and danced in fantastic blotches; the screen turned to a welter of black, threatening shadows; became a useless maze of ever-changing forms. Keith mouthed curses as he stared at it; he now had nothing by which to judge his progress, to maneuver the submarine, save directional instruments and, perhaps, chance sc.r.a.pings of the tunnel's ragged walls against the outer hull. The _NX-1_ was running a gauntlet of immeasurable danger, her only a.s.surance of success being the fact that a larger craft had preceded her.

But how far, Keith wondered, had that ship preceded her? How was he to know that it had gone straight through? There might be a dozen different turnings in this tunnel: the submarine could easily tilt head-on against a jagged rock and puncture her hull. There might be mines planted directly in their course; he might be swimming straight into some hideous ambuscade.

He drove these thoughts from his mind. The pa.s.sage had to be made on the fickle authority of the senses; and, realizing this, Wells took the helm into his own hands. Graham was posted at the location chart, with instructions to report the red light if it showed.

Down below, the Edsel electrics were humming very softly; the men stood vigilantly at posts. On their brows were little beads of sweat, and here and there a hand clenched nervously. All knew they were in a tight place; otherwise they were ignorant of where their commander was leading them. Occasionally a long, shivering rasp ran through the ship as her hull nudged the rough tunnel wall. Then the course rudders would swing gently over; and perhaps, almost immediately, another grinding cry of rock and steel would come from the other side. Then would come quickly indrawn breaths as the rudders swung again and the humming silence droned on.

The sc.r.a.pings came quite often. Often, too, the motors would go silent altogether, and the _NX-1_ would rest almost motionless as her commander felt for an opening. It was a tense, nerve-wringing ordeal.

The silence, the waiting, the dainty sc.r.a.pings were maddening.

Keith Wells' skin was p.r.i.c.kling. He kept only fingertips on the tiny helm: he was playing that uncanny sixth sense of the submarine commander. When it misled him, the rasping rock groaned out, scarring the submarine's smooth skin. Generally, the tunnel was straight; but each time he heard his ship rub against some exterior obstruction, his teeth went tight--for who knew but what it might be a mine?

They had penetrated perhaps a half-mile when Graham, eyes steady on the teleview, reported: "Light growing, sir!"

Wells saw that the screen was filling with a soft, faintly glowing bluish color. The walls of the tunnel became visible, and he noted that they were widening out, funnel-like. He dared to increase speed slightly. Three minutes later he saw that the blue illumination was seeping from the end of the tunnel. They continued out.

"Thank G.o.d, we're through!" he muttered to Graham. "You see, I was right! It's an underground sea--and we're at the top of it." For the instruments indicated a depth beneath them of roughly three miles.

They were in, evidently, a large cavern, of vast length and depth.

The _NX-1_ continued slowly forward, two pairs of eyes intent on her teleview screen. Keith jotted down the tunnel's position, and the funnel-shaped hole sank away behind their slow screws. And then, upon the location chart, a faint red dot suddenly glowed!

It was upon them in a flash. A small tube of metal, shaped somewhat in the form of the big octopi submarine, had darted up from below, hovered a second close to them, and then, almost before they realized they were being surveyed, sped back into the mysterious depths from which it had come.

"A lookout, I suppose," Keith muttered, breathing more easily.

"Couldn't have held more than two of those creatures.... Well, the alarm's out, I guess, Graham, but it can't be helped. Let's see what it's like down below."

They plunged steadily down, then ahead. And presently there grew on the teleview vague forms which widened their eyes and made their breath come quicker. Keith had guessed the tunnel led to a civilization of some kind, but he was not prepared for the sight that loomed hazily through the soft blue water.

Strange, moundlike shapes appeared far below, mounds grouped in orderly rows and cl.u.s.ters, with streets running between them, thronged with tiny, spidery dots. Octopi! It was, the commander realized, a city of the monsters--a complete city like those of surface peoples!

For several miles in every direction the water-city spread out, farther than the teleview could pierce. Wells marveled at this separately developed civilization, this deep-buried realm of octopi whose unexpected intellectual powers had permitted such development.

Perhaps, he pondered, this city was only one of many; perhaps only a village. He could but vaguely glimpse the queer mound buildings, but saw that they were of varying height and were filled with dark round entrance holes, through which the creatures streamed on their different errands....

He saw no schools of fish around. "I guess they're been all killed off, or eaten," he commented to the wonder-struck Graham. "Probably the octopi have separate hatcheries where they raise them for food."

"But--good Lord!" the first officer exclaimed. "A city--a city like ours! Down here, filled with octopi!..."

"Yes," answered Wells grimly, "and this 'city' may only be a small settlement; there may be scores of these places. We'd better continue ahead now that we're here; for we've got to get all the information we can. I only hope these monsters haven't more than one big submarine.

We can expect an attack any minute...."

The _NX-1_ pressed on. The city dropped behind. A breathless tenseness had settled down over the submarine; she was proceeding with utmost caution, her anxious officers alert at the location chart. The great fear that tormented them was that they might be attacked, not by one, but by a fleet of the octopi ships....

Then, at the rim of the chart, a red dot appeared! It grew rapidly, charging down on them at great speed. The spot was large; this was no small sentry boat! At once the alarm bell shrilled its warning; the crew below left their posts and raced to the control room. With sure mechanical fingers the emergency system gripped the valve handles and motor levers; Keith swung the _NX-1_ onto a level keel, straightened her out, and decreased speed still more. Giving the rods of the motor and rudder controls to Graham, he moved to the small lever which would unleash his bow torpedoes, and fingered it lightly. The _NX-1_ was ready for action.

Scarcely had the men reached the small control room than the familiar electric charge tingled. They stared wonderingly at each other, half afraid. No one seemed hurt. One hand on the torpedo lever, Wells watched his charts and instruments. He thanked G.o.d that there was only one of the enemy.

The ray's shock came again--and stronger. The red dot was practically upon them. The screen was still empty. Coolly, Keith slowed the submarine to a dead stop. The crimson stud came closer....

And then he saw it. It was the same fearsome, hulking form. The same curving windows, dark and lifeless. The same k.n.o.bs on its bow, one now leaping and pulsing with the paralyzing glow. At a distance of a few hundred feet the octopi ship swerved to a halt, dousing the NX-1 with its ray unceasingly. Again those two underwater craft, so oddly contrasted, were face to face. And again the weapon that had once struck the American ship's crew down at their posts was directed full onto the _NX-1_.

But it was harmless! It merely tingled, and did not paralyze! The control room sheathing held it out stoutly. The men's faces showed overwhelming relief.

Keith smiled grimly. Now, at least, he had the devils where he wanted them; now it was his turn to strike with a--to them--terrible, mysterious weapon. They had attacked; had failed--and now he could square up for Hemmy and send a pair of torpedoes into that ship of hideous tentacles.

"Port five!" The ship swerved slightly. "Hold even!" The enemy craft was very close. The _NX-1's_ bow tubes were sighted in direct line.

Her torpedoes could not possibly miss. This time, destruction for the octopi ship was inevitable....

Keith Wells gripped the lever that held the torps in leash.

"_Wait!_"