Howard felt, as Agvur spoke, the chill of a sinister menace; but in the weirdness of the ceremony that followed, he almost lost his apprehension of personal peril.

One by one, from the further end of the row in which he was standing, the silent Oumnis went forward and circled the strange plant, walking slowly within a few feet of the inert branches of poisonous green that resembled sleepy, half-coiled serpents. The Roccalim preserved a torpid stillness, without the least sign of animation, as Oumni after Oumni finished his perilous circuit and retired to the further side of the room, there to stand and watch the perambulations of the others.

About twenty of the white Immortals had undergone this ordeal, when Howard’s turn came. Resolutely, with a sense of unreality and grotesquery rather than actual danger, he stepped forward and began his circuit of the living plant. The Oumnis looked on like alabaster statues; and all was utterly still and silent, except for a muffled, mysterious throbbing as of underworld machinery at a distance.

Howard moved on in an arc, watching the green branches with a growing tenseness. He had gone half the required distance when he felt, rather than saw, a flash of swift, intense light that appeared to stab downward from the cavern roof and strike the lumpish yellow bole of the Roccalim. The light faded in the merest fraction of time, leaving Howard in doubt as to whether he had really seen it.

Then, as he went on, he perceived with startled horror that the trailing tentacular boughs had begun to twitch and quiver, and were lifting slowly from the floor and waving toward him. On and on they came, rising and straightening, like a mass of ropy kelp that flows in an ocean-stream. They reached him, they slithered with reptilian ease about his body, and touched his face with their venomous-looking tips, clammy and inquisitive.

Howard drew back, wrenching himself away from the waving mass, and found Agvur at his elbow. The face of the Mercutian was touched with an unearthly gloating; and his iridescent locks floated upward, quivering with weird restlessness, like the Roccalim branches.

At that moment, it came to Howard that his fate had been predetermined from the beginning; that the swift, evanescent flash of light, proceeding from an unknown source, had perhaps served in some manner to irritate the living plant and provoke the action of its tentacular limbs.

Swift anger flared in the earth-man, but he repressed it. He must be cautious, must watch for an opportunity—even the slimmest—of escape. By giving the impression that he was resigned, he might throw his captors off their guard.

He saw that a number of new Mercutians, equipped with long glittering tubes like blow-pipes, had entered the cavern and were surrounding him. The companions of his late ordeal had begun to disperse in various directions.

“I am sorry,” said Agvur, “that the choice should have fallen upon you. But your death will be swift—and the time is near at hand. The fusing must be completed, and the metal must be poured off and cast in thin, malleable sheets, before the next term of darkness and slumber, which will occur in little more than an hour. During this term—three hours out of every thirty-six—the transmitted sunlight is excluded from all our chambers and passages; and most of our machinery, which derives its power from light, is rendered inactive.”

III

In mingled horror and dumbfoundment, Howard was taken through an opposite entrance of the Roccalim’s cavern and along a sort of hall which appeared to run parallel with the one in which the incline had ended. Agvur walked at his side; and the Oumni guards were grouped before and behind him. He surmised that the glittering, hollow tubes they carried were weapons of some novel type.

As they went on, the mysterious throbbing noise drew steadily nearer. Howard saw that the far end of the corridor was illumined with a fiery red light. The air was touched with queer metallic odors; and the temperature, which had heretofore been one of unobtrusive warmth, seemed to rise slightly.

At one side, through an open door in the passage wall, as they neared the source of the red light, Howard saw a large room whose further end was filled with lofty banks of shining cylinder-shaped mechanisms. In front of these mechanisms, a solitary Mercutian stood watching an immense pivot-mounted ball which appeared to be filled nearly to the top with liquid blackness, leaving a crescent of bright crystal. Near the ball, there was a sort of inclined switchboard, from which arose many rods and levers, made of some transparent material.

“The lighting apparatus of all our caverns is controlled from that room,” said Agvur, with a sort of casual boastfulness. “When the ball has turned entirely black, the sunlight will be turned off for the three-hour period, which gives us all the sleep and rest we require.”

A moment more, and the party reached the end of the passage. Howard stood blinking and breathless with wonder when he saw the source of the dazzling red light.

He was on the threshold of a cavern so enormous that its roof was lost in luminosity and gave the effect of a natural sky. Titanic machines of multiform types, some squat and ungainly and others like prodigious bulbs or huge inverted funnels, crowded the cavern-floor; and in the center, towering above the rest was a double, terrace-like platform of sable stone, thirty feet in height, with many pipes of dark metal that ramified from its two tiers to the floor, like the legs of some colossal spider. From the middle of the summit, the ruddy light arose in a great pillar. Gleaming strangely against the fiery glow, the forms of Oumnis moved like midges.

Just within the entrance of the Cyclopean room, there stood a sort of rack, from which hung a dozen suits of the mouffa-metal. Their construction was very simple, and they closed and opened at the breast, with odd dove-tailings. The head was a loose, roomy hood; and the metal had somehow been rendered transparent in a crescent-like strip across the eyes.

The suits were donned by Agvur and the guards; and Howard noticed that they were extremely light and flexible. He himself, at the same time, was ordered to disrobe.

“The mouffa mixture, during the process of fusing, gives off some dangerous radiations,” said Agvur. “These will hardly matter in your case; and the suits of finished metal will protect my companions and me against them, even as against the deadly solar rays.”

Howard had now removed all his clothes, which he left lying near the rack. Still pretending his resignation, but thinking desperately all the while and observing closely the details of his situation, he was led along the crowded floor, amid the sinister throbbing and muttering of the strange engines. Steep, winding stairs gave access to the terraced mass of dark stone. The earth-man saw as he went upward, that the lower tier was fitted with broad, shallow moulds, in which doubtless the metal would run off from the furnace to cool in sheets.

Howard felt an almost overpowering heat when he stood on the upper platform; and the red glare blinded him. The furnace itself, he now saw, was a circular crater, fifteen feet across, in the black stone. It was filled nearly to the rim with the molten metal, which eddied with a slow maelstrom-like movement, agitated by some unknown means, and glowing unbearably. The black stone must have been a non-conductor of heat, for it was cool beneath Howard’s bare soles.

On the broad space about the furnace, a dozen Oumnis, all sheathed in the glittering mouffa, were standing. One of them was turning a small, complicated-looking wheel, mounted obliquely on a miniature pillar; and as if he were regulating the temperature of the furnace, the metal glowed more brightly and eddied with new swiftness in its black crater.