"From some records we captured, his name was Ivan Saranoff. I never saw him."

"Saranoff?" said Dr. Bird thoughtfully. "The name seems familiar. Where have I--Thunder! I know now. He was at one time a member of the faculty of St. Petersburg. He was one of the leading biologists of his time.

Carnes, we've found our man."

"If you are thinking of Saranoff, I am afraid you are mistaken, Doctor,"

said Commander Minden. "Neither he nor his submarine have ever been heard of since and it has been generally conceded that they were lost at sea. We had some pretty rough weather just after that affair."

"Rough weather doesn't mean much to a sub, Commander. I expect that he's our man. At any rate, the place we want to go is the end of that tunnel."

"I'm at your service, Doctor."

"Carnes, get the location of that tunnel entrance from Commander Minden and order the _Minneconsin_ to proceed north along the coast to that vicinity and stand by for radio orders. I am going to telephone Mitch.e.l.l Field and get a plane. We have no time to lose."

The plane from Mitch.e.l.l Field roared down to a landing, and Carnes, Dr.

Bird and Commander Minden dismounted from the rear c.o.c.kpit and looked around. They had landed in a smooth field at the base of a rise almost rugged enough to be called a mountain. A group of three men were standing near them as they got out of the plane. One of the men approached.

"Dr. Bird?" asked the newcomer. "I am Tom Harron, United States Marshal.

These two men are deputies. I understand that I am to report to you for orders."

"I'm glad to know you, Mr. Harron. This is Operative Carnes of the Secret Service and Commander Minden of the Coast Guard. We are going to explore an underground cavern that is located in this vicinity."

"Do you mean the one where they used to smuggle aliens? That is closed up. I was in charge of that work and we closed it tight as a drum two years ago."

"Can you find the entrance?"

"Sure. It isn't over a mile from here."

"Lead the way, then. We want to take a look at it."

The marshal led the way toward the eminence and took a path which led up a gully in its side. He paused for a moment to take his bearings and then turned sharply to his left and climbed part way up the side of the ravine.

"Here it is," he announced. An expression of astonishment crossed his face and he examined the ground closely. "By Golly, Doc," he went on as he straightened up, "this place has been opened since I left it!"

Dr. Bird hurried forward and joined him. The heavy stone and concrete with which the entrance to the cavern had been sealed were undisturbed, but in the side of the hill was set a steel door beside the concrete.

There was no sign of a keyhole or other means of entering it.

"Was this steel door part of your work?" asked Carnes.

"No, sir, it wasn't. We sealed it solid. That door has been put there since."

Dr. Bird closely examined the structure. He tapped it and went around the edges and then straightened up and took a small pocket compa.s.s from his pocket and opened the case. The needle swung crazily for a moment and then pointed straight toward the door.

"A magnetic lock," he exclaimed. "If we could find the power line it would be easy to force, but finding that line might take us a week. At any rate, we have found out what we were after. This is their base from which they are operating. Mr. Harron, I want you to station a guard armed with rifles at this door day and night until I personally relieve you. Remember, until I relieve you, in person. Verbal or written orders don't go. Capture or kill anyone who tries to enter or leave the cavern through this entrance. Just now we'll find that cavern more vulnerable from the sea end, and that is where I mean to attack. We'll force that door and explore from this end later. Commander Minden, you may stay here with Mr. Harron, if you like, or you may come with Carnes and me.

We are going on board the _Minneconsin_."

The Mitch.e.l.l Field plane roared to a take-off and bore south along the coast. Half an hour of flying brought them in view of the battleship steaming at full speed up the coast. Dr. Bird radioed instructions to the ship, and an hour later a launch picked them up from the beach and took them out. As soon as they were on board they resumed their progress, and in two hours the peak that Dr. Bird had marked as a landmark was opposite.

"Steam in as close to the sh.o.r.e as you can safely," he said, "and then lower us. Once we are down, you will be guided by our telephoned instructions. Come on, Carnes, let's go."

The detective followed him into the sphere as the _Minneconsin_ edged up toward the sh.o.r.e. The huge ball was lifted from the deck and lowered gently into two hundred fathoms of water. It was pitch dark at that depth, and Dr. Bird switched on one floodlight and studied the cliff which rose a hundred yards from them.

"We have missed the place, Carnes," he said. "We'll have them pull us up a few hundred feet and then steam along the coast."

He turned to the telephone and the sphere rose while the battleship steamed slowly ahead, the vitrilene ball following in her wake. For a quarter of a mile they continued on their way, and then Dr. Bird halted the ship.

"What depth are we?" he asked. "Eighty fathoms? All right, lower us, please."

The ball sank until it rested on the sea bottom, and Dr. Bird turned on two additional floodlights and studied the surroundings. The bed of the ocean was literally covered with lobster and crab sh.e.l.l, with the bones of fish scattered here and there among them. A few bones of land animals were mixed with the debris and Carnes gave a gasp as Dr. Bird pointed out to him a diving helmet.

"We are on the right track," said the scientist grimly. He stepped to the telephone and ordered the sphere raised to one hundred fathoms. The ship moved forward along the coast until Dr. Bird again stepped to the telephone and halted it. Before them yawned the entrance to the underground tunnel. It was about two hundred feet high and three hundred across, and their most powerful beams would not penetrate to the end of it. A pile of debris could be seen on the floor of the tunnel and Carnes fancied that he could see another diving helmet among the litter.

Dr. Bird pointed toward the side of the cavern.

"See those floodlights fastened to the cliff so that their beams will sweep across the mouth of the tunnel when they are lighted?" he said.

"Apparently the cave is used as a prison and the light beams are the bars. The creature is not at home just now or the bars would be up. My G.o.d! Look at that, Carnes!"

Carnes stared and echoed the Doctor's cry of surprise. Clinging to a shelf of rock which extended out from the wall of the cavern and half hidden among the seaweed was a huge marine creature. It looked like a huge black slug with rudimentary eyes and mouth. The thing was fifty feet in length and fully fifteen feet in diameter. It hung there, moving sluggishly as though breathing, and rudimentary tentacles projecting from one end moved in the water.

"What is it, Doctor?" asked Carnes in a voice of awe.

"It is a typical trochosphere of the giant octopus, the devil fish of Indian Ocean legend, multiplied a thousand times," he replied. "When the octopus lays its eggs, they hatch out into the larval form. The free swimming larva is known as a trochosphere, and I am positive that that is what we see; but look at the size of the thing! Man alive, if that ever developed, I can't conceive of its dimensions!"

"I have seen pictures of a huge octopus pulling down a ship," said Carnes, "but I always fancied they were imaginary."

"They are. This monstrosity before us is no product of nature. A dozen of them would depopulate the seas in a year. It is a hideous parody of nature conceived in the brain of a madman and produced by some glandular disturbance. Saranoff spent years in glandular experimentation, and no doubt he has managed to stimulate the thyroid of a normal octopus and produce a giant. I fancy that the immediate parent of the thing before us was of normal size, and so, probably, are its brothers and sisters.

The phenomenon of giantism of this nature occurs in alternate generations and then only in rare instances. Its grandparent may not be far away, however. I wish it was safe to use a submarine to explore that cavern."

"Why isn't it?"

"Any creature powerful enough to pull the _Arethusa_ under water would crush a frail submarine without effort. Anyway, a Navy sub isn't built for under-water exploration like this ball is. The window s.p.a.ce is quite limited and they aren't equipped with powerful floodlights. I would like to be able to reach that thing and destroy it, but it can wait until later. The best thing we can do is to put out our lights and wait."

His hand sought the light switch, and the globe became dark. Only a tiny glimmer of light came down to them from the surface, a hundred fathoms above. In the darkness they stared into the depths of the sea.

For an hour they waited and then Dr. Bird grasped Carnes by the shoulder and pointed. Far in the distance could be seen a tiny point of light. It wavered and winked and at times disappeared, but it was gradually approaching them. Dr. Bird stepped to the telephone and the _Minneconsin_ moved a hundred yards further from the sh.o.r.e. The light disappeared again as though hidden by some opaque body. Their eyes had become accustomed to the dim light and they could dimly see a long snake-like body approach the globe and then suddenly withdraw.

The light appeared again only a few hundred yards away. The water swirled and the sphere swayed drunkenly as some gigantic body moved past it with express train speed and entered the mouth of the cavern. The light turned toward them and they could see the dim outlines of a small submarine on which it was mounted. Another rush of water came as the object which had entered the cave started to leave it, and the light swung around. It bore on a huge black body, and was reflected with a red glow from huge eyes, and the creature backed again into the cave. Back and forth across the mouth of the cavern the light played, and the watchers caught a glimpse of a huge parrot beak which could have engulfed a freight car. From the cavern projected twisting tentacles of gargantuan dimensions, and red eyes, thirty feet in diameter, glared balefully at them. For several minutes the light of the submarine played across the mouth of the cave, and then the floodlights on the cliff sprang into full glow and bathed the ball and the mouth of the tunnel in a flood of light.

Before their horrified gaze was an octopus of a size to make them disbelieve their eyes. The submarine had moved up to within a few feet of them, and the light from it played full on the ball. The submarine maneuvered in the vicinity, keeping the ball full in the beam of its light, and then drew back. As it did so, the floodlights on the cliff died out and the beam of the submarine's light was directed away from them. Dr. Bird jumped to the telephone.