closed the switches and hurled your bodies to where a receiving-station on this plane integrated them again."

So they were not at the bottom of the ocean. They were—stupendous thought—living in a new world of matter!

"Spiro suspected our plans," continued Zoro. "He isolated us in our laboratories, and, by means of a crystal tube, went through to the tunnel, tore up a section of track, and wrecked the submarine-car. But his act was only partially successful. You two escaped death; you are here; you are ready to keep faith and fight in our service."

"We are ready to fight," assented Miles and Ward. The situation was certainly an unusual one, and one they did not clearly understand; but theirs was the simple code of the mercenary soldier—they would fight for whoever hired them, and be loyal as long as their wages were paid.

"Then there is no time to lose," exclaimed Zoro. "Already our blood grows thin. You must go back to the wrecked submarine and retrieve your weapons."

"But how?"

"There is a sending tube in the next compartment."

They followed Zoro through lofty rooms filled with amber light until they came to one wherein were assembled the rest of the Heads. Zoro spoke to them swiftly in a strange, flowing tongue. Then he conducted the two Americans to a crystal chamber at the end of the room and bade them enter it. The vibrant light caressed their limbs.

"When I close this door," he said, "you will find yourselves back in the tunnel. Board one of the submarine-cars on the siding and proceed to the wreck." He gave them detailed instructions how to operate the car. "Then get your weapons and return. Do you understand?"

They nodded.

"The workers possess no arms the equal of machine-guns and bombs. They will be at your mercy. Remember that you are fighting for our lives and that, if you save them, your reward will be great. Fear nothing."

The door closed. After a moment there was a blinding flash, a moment of swooning darkness, and then they were staring through transparent walls into the phosphorescent gloom of the underseas crypt. Suddenly, what they had recently undergone seemed the product of an illusion, a dream. Ward shook himself vigorously. "I guess it was real enough," he said. "Let us see if the car works."

They ran out to the wreck and returned without trouble. The machine-gun was mounted for action and the gas-bombs slung over their shoulders in convenient bags. "All right," said Miles tensely, "let us go."

Again they entered the crystal chamber; again there was the flash of light and the sensation of falling into darkest space. Then, in a moment it seemed, they were stepping into the hall from which they had fled pursued by the green men—only for the second time, to be confronted by a crowd of hostile giants. "Don't fire, Kid!" yelled Ward. "It's no use to kill them uselessly. Give them the bombs!"

Disconcerted by the attack of tear-gas, the green men broke and fled. "After them," panted Ward: "we've got them on the run!"

Thrilling to the lust of battle, the two Americans emerged into an open square. They had little time to note the odd buildings and strange statues. Coming towards them with leveled weapons, the nature of which they did not know, was a band of short men—that is, short in comparison with the greenish giants. Behind this company appeared still another, and another. Tear-gas was useless to stop their onward rush. "All right," yelled Miles, "it's lead they want!"

The machine-gun spat a hail of bullets. Before the first withering blast the swarthy men recoiled in confusion. Then a second volley scattered them like chaff. Miles and Ward were conscious of no pity for the dead and wounded lying on the pavement of yellow stone. This was their profession, the stern business of which they were masters. In France they had seen worse sights, and in Nicaragua and Mexico. They swept destructively out of the square and into a long tree-lined avenue. This might be another world or dimension but its trees looked not unlike those of tropical America.

In a short while the radiating streets were cleared of crowds and the cries of the mob died away. Miles and Ward paused in the shadow of an overhanging wall and wiped their faces. "That was quick work, all right," said Ward; and, even as he said it, the wall seemed to fall upon their unprotected heads and crush them into unconsciousness....

Out of a sick darkness they came. At first they thought they were confronting Zoro. Then, as the mists of unconsciousness cleared from aching heads, they perceived that they were in a vast hall crowded with swarthy men in short tunics, and with greenish giants wearing nothing but breech-clouts and swinging short clubs. The fierce eyes of the greenish giants were upon them, and the vengeful ones of the swarthy men. But the desire of both to rend and tear was held in check by the dominant head emerging from a tubular container mounted upon a wheelchair. The Americans stared. This was not the head of Zoro. No!

"The head of Spiro," thought Miles and Ward with sinking hearts.

They had fallen into the power of the leader of the insurgent workers!

Spiro—for it was indeed he—regarded them with pitiless eyes. His English was slower and not as fluent as that of Zoro, and his words harder to understand.

"You Americans, beings of another world, have come here at the bidding of the Heads to slay and kill for gold."

He paused. "I who for three years studied your country, learned its language, history, did not believe men of your race could be so vile."

He paused again, and Ward broke out hotly, "It is true that we came here to fight for gold, but who are you to speak of vileness? Have you not turned on the Heads, your benefactors, now your brothers, who raised you to their height? Are you not leading a revolt of the workers which would deny them the means of sustaining life? Are you not seeking to perpetrate—murder?"

Spiro regarded him slowly. "Is it possible you are in ignorance of what those means are? Listen, then, while I tell you the hideous truth. Since the dawn of our history, until the present moment, the Heads have maintained their lives by draining blood from the veins of thousands of Apexans yearly!"

The Americans' faces whitened. "What do you mean?" breathed Ward.

"I mean that the artificial blood pumped by mechanical hearts through the brains of the Heads—yes, and that is now being pumped through my own!" cried Spiro bitterly—"is manufactured from human blood. Human blood is the basis of it. And to get that blood every Apexan must yield his quota in the temple. Slowly but surely this practice is sapping the vitality of the race. But though the Apexans realized this they were afraid to speak against the custom. For the Heads were worshipped as gods; and when the gods spoke, blasphemers died—horribly."

Miles and Ward shuddered.

"Even I," went on Spiro, "denounced blasphemers and thought it holy that each should yield a little of his blood to the Almighty Ones. Then I woke from darkness to find myself—a Head. At first I could not understand, for I was in love with Ah-eeda—and can a machine mate? But it is true that love is largely desire, and desire of the body. With the death of the body, desire died; and it may be that pride and ambition took its place. But, for all that, there were moments when I remembered my lost manhood and dreamed of Ah-eeda. Yes, though the laboratory of the Heads revealed wonders of which I had never dreamed, though I looked into your world and studied its languages and history, though I was worshipped as a god and endless life stretched ahead of me—nevertheless, I could see that the strength of my race was being sapped, its virility lost!"

His voice broke. "In the face of such knowledge what were immortality and power? Could they