lthough puzzled by the Hawk's promise, Leithgow could only put his trust in it and go ahead with the preparations as he had been directed. He took two of his three laboratory assistants off their hurried manufacture of quantities of the V-27, and with Ku Sui went out into the air-car. Passing by way of tube and lake and air, they were quickly inside the dome on the asteroid, and then into Ku Sui's laboratory, where Friday waited on guard.

Completely docile and friendly, the Eurasian indicated the various instruments and devices he would need for the operations, and these were transported quickly. Then came the case of coordinated brains. Dr. Ku detached in connections with expert fingers, and all but Leithgow took a corner and carried it with infinite care to the air-car outside.

"Do I stay here, suh?" Friday asked the Master Scientist in a whisper. Though informed of the change in Dr. Ku effected by the V-27, he was still very suspicious of him. "Seems to me he's a bit too meek and mild, suh. I think I ought to go down and watch him."

Eliot Leithgow did not quite know what answer to give. The Eurasian forced the decision.

"I will need," he observed, in his new, frank voice, "all the assistance you can possibly give me. I am faced by a tremendous task, and the use of every man will be necessary. I would suggest, Master Leithgow that the Negro be brought down."

And so Friday came and the asteroid was left unguarded. A mistake, this turned out to be, but under the circumstances Eliot Leithgow could hardly be blamed for it. There was so much on their minds, so much work of vital importance, so desperate a need for speed, that quite naturally other considerations were subordinated. The asteroid, to the naked eye, was invisible; it could attract no attention; its occupants had all been disposed of. Certainly it seemed safe enough to leave it unguarded for a while.

However, Eliot Leithgow took one precaution. Down in his own laboratory again, in the midst of the work of transferring Dr. Ku's operating equipment from the air-car, he called aside one of his assistants and instructed him to go and survey the asteroid through the infra-red device every ten minutes: and with this order the old scientist dismissed the matter from his mind, and turned all his energies to preparing the laboratory for the operations.

nder Ku Sui's directions his cases of equipment were brought in and arrayed, and the various drills and delicate saws, and such other instruments as worked by electricity, were connected. Everything was sterilized. Rapidly the plain, square room assumed the appearance of an operating arena, the five tables in the center, spotlessly white and clean under the direct beams of the tubes hanging from the ceiling, at the head of every table a stand on which were containers of antiseptics, bottles of etheloid, a breathing cone, rolls of gauze and other materials, and along the edge of the stand identical, complete sets of fine instruments.

The case of coordinated brains was brought into the laboratory last. The inner liquid was now dark and apparently lifeless; to the casual eye, it would not have seemed possible that the five grayish mounds immersed in the liquid held life. And, indeed, Leithgow looked at them doubtfully.

"Are you sure they're still alive? Do you think there's still time?" he asked Dr. Ku.

The Eurasian picked up a long, slender, tubelike instrument with a dial topping it. Then, going to the brain-case, he touched a cleverly concealed catch and a square pane set in the top of the case swung back. He dipped the instrument he held into the liquid, and for a moment stood silent, watching the dial. Then he took it out, re-closed the pane and turned to Leithgow.

"A test," he explained. "The indicator, interpreted means we have about forty-eight minutes in which to complete the first phase of the transplantation of the brains into human heads. It might be done if we start in eight minutes. But the human heads—?" He paused.

"Eight minutes!" said Leithgow worriedly. "Eight minutes for Carse to come! He promised the bodies, but ... well, we can only go ahead with the preparations and trust to him. Is everything ready?"

"All but my assistants. I had better see them now."

he Master Scientist issued an order to one of his men, and presently the four white assistants of Dr. Ku were led into the laboratory. For these men, no V-27 was needed; their brains were utterly subservient to Dr. Ku Sui, and his orders they would obey unquestioningly, no matter what the work. There was no danger from them.

They stood motionless, their eyes fastened on their master, as he spoke to them.

"Brain operations," he said. "These"—he indicated the case—"are to be transplanted again into human heads. You have done work similar to it before; you know the routine. But now it must be quick. Synchronize your speed with mine; I will be working very rapidly, and it is vital that you be in harmony with me every instant. When the bodies come, you will prepare the heads: and then you will attend me through every step. You understand." He turned to the old scientist. "Operating gowns, gloves, masks, Master Leithgow?"

"I have your own. Over there. Your black costume is among them."

But Leithgow's answer was abstracted. Four minutes for Carse to come! Or else, everything lost! He busied himself helping the four surgeons and two of his own assistants into the white, sterilized gowns, and the masks that left only the eyes free and the skin-tight rubber gloves, but his mind was not with his actions. The old man looked very frail now; his age showed in the deep lines now eminent on his face. Three minutes—swiftly two....

"At least," observed Ku Sui, "we have one body ... the coolie. I had better start immediately on him."

"Bring him out," Leithgow instructed one of his men. "One brain will be saved. But—there! Thank God! Hear that? Coming down the passage? It's Carse, returning!"

t was Carse. He and Ban Wilson, coming down the passage from the top of the tree-shaft. Everyone in the laboratory could hear plainly the heavy, sliding tread of the great space-boots. Eliot Leithgow was first to the door. He opened it, peered through eagerly and called:

"Carse? You've got them?"

"Yes, Eliot. Here—we need help."

The Hawk's voice sounded weary. Friday and the scientist ran down the passageway until they reached the adventurer. In the faint light, they saw he was carrying a limp body. He laid it carefully down on the floor.

"Ban's coming down with another," he said, "and there are two more above. Go up and get them, Friday."

The Negro started to obey. But Eliot Leithgow did not move, did not utter a sound. He stood staring at the body Carse had laid down. The parchmentlike skin of his face seemed to whiten; that was all; but he winced and slowly brushed his eyes with his hands when, in a moment, Ban Wilson floated down the shaft and, approached with a second unconscious body.

At last Leithgow whispered:

"They're all—like that, Carse?"

"Yes," answered the emotionless voice. "There were two others, but we let them go. They were worse." The gray eyes looked steadily at Eliot Leithgow. "I know," the Hawk said. "It's horrible—but it can't be helped. It was these or nothing. There was no choice."

Hawk Carse had fulfilled his promise. He had brought back four isuanacs.