around.

They had carefully followed the instructions in the log. They were at the exact place noted there: checked and double-checked. The radio receiver was tuned to the wave-length given in the log. But of Ku Sui, nothing.

And yet, in a way, he was with them. His enigmatic personality, his seldom-seen figure was very present in their minds, and with it were overtones of all the diabolic cunning and suave ironic cruelty that men always associated with him. "He comes out of darkness, out of empty space...." Friday licked his lips. He was not built for mental strain: his lips kept drying and his tongue was as leather.

A little sputtering sound tingled the nerves of the three waiting men, and as one their eyes went to the radio loudspeaker. A contact question was being asked in the usual way:

"Are you there, Judd? Are you there, Judd? Are you there, Judd?"

The voice was not that of Ku Sui. It was a dead voice, toneless, emotionless, mechanical.

"Are you there, Judd?" it went on, over and over.

"The mike switch, Friday," the Hawk said, and then was at Sako's side, his ray-gun transfixing the man with its threatening angle. "Play your part well," was the whisper from his lips.

The switch went over with a click. Trembling, Sako faced the microphone.

"This is Sako," he said.

"Sako?" the dead voice asked. "I want Judd. Where is Judd?"

"Judd is dead. The trap failed, and there was a fight on Iapetus. Judd was killed by Carse, and most of the others. Only two of us are left, but we have Carse and the negro, prisoners, alive. What are your instructions?"

A half minute went by, and the three men hardly breathed.

"How do we know you are Sako?" said the voice at last. "Give the recognition."

"The insignia of Dr. Ku Sui?"

"Yes. It is——"

Carse's ray-gun prodded the stomach of the sweating Sako.

"An asteroid," he said hastily, "in the center of a circle of the ten planets."

The unseen speaker was quiet. Evidently he was conferring with someone else, probably Ku Sui.

"All right," his toneless voice came back at last. "You will remain motionless in your present position, keeping your radio receiver open for further instructions. We are approaching and will be with you in thirty minutes."

Carse motioned to Friday to switch off the mike. Sako sank limply into a chair, soaked with perspiration.

"Now we must wait again," the Hawk murmured, crossing his arms and scanning the visi-screen.

They had heard from Ku Sui, but that had not answered the old tormenting question of how he would come. It was more puzzling than ever. The visi-screen showed nothing, and it should have shown the Eurasian's decelerating ship even at twice thirty minutes' time away. They looked upon the same vista of Jupiter and his satellites, framed in eternal blackness; there was no characteristic steely dot of an approaching ship to give Carse the enemy's position and enable him to shape his plan of reception definitely.

Twenty minutes went by. The strain the Hawk was under showed only in his pulling at the bangs of flaxen hair that covered his forehead as far as the eyebrows. He had, from Judd's words, expected a mystery in Ku Sui's approach. There was nothing to do but wait; he had made what few plans and preparations he could in advance.

Friday broke the tense silence in the control cabin. "He's got to be somewhere!" he exploded. "It isn't natural for the screen not to show nothin'! Isn't there somethin' we can do?"

The Hawk was surprisingly patient. "I'm afraid not," he said. "It's invisibility he's using, or else the fourth dimension, as Judd said. But we've got one good chance. He'll send more instructions by radio, and surely, after that, his ship will appear——"

A new voice, bland and unctuous, spoke in the control cabin from behind the three men.

"Not necessarily, my honored friend Carse," it said. "You will observe there is no need for a ship to appear."

Ku Sui had come.

CHAPTER III

The Wave of a Handkerchief

He stood smiling in the door-frame leading aft to the rear entrance port. There was all grace in his posture, in the easy angle at which one arm rested against the side bulkhead, in the casual way in which he held the ray-gun that bored straight at Carse. Height and strength he had, and a perfectly proportioned figure. Beauty, too, of face, with skin of clearest saffron, soft, sensitive mouth and ascetic cheeks. His hair was fine and black, and swept straightly back from the high narrow forehead where lived his tremendous intelligence.

It was his eyes that gave him away, his eyes of rare green that from a distance looked black. Slanting, veiled, unreadable beneath the lowered silky lashes, there was the soul of a tiger in their sinister depths. It was his eyes that his victims remembered....

"So you have arrived, Dr. Ku," whispered Hawk Carse, and for a second he too smiled, with eyes as bleak and hard as frosty chilled steel. Their glances met and held—the cold, hard, honest rapier; the subtle perfumed poison. The other men in the cabin were forgotten; the feeling was between these two. Strikingly contrasted they stood there: Carse, in rough blue denim trousers, faded work-shirt, open at the neck, old-fashioned rubber shoes and battered skipper's cap askew on his flaxen hair; Ku Sui, suavely impeccable in high-collared green silk blouse, full-length trousers of the same material, and red slippers, to match the wide sash which revealed the slender lines of his waist. A perfume hung about the man, the indescribable odor of tsin-tsin flowers from the humid jungles of Venus.

"You see I meet you halfway, my friend," the Eurasian said with delicate mock courtesy. "A surpassing pleasure I have anticipated for a long time. No, no! I see that already I shall have to ask you a small favor. A thousand pardons: it's my deplorable ability to read your mind that requires me to ask it. Your so justly famed speed on the draw might possibly overcome this advantage"—he raised his ray-gun slightly—"and, though I know you would not kill me—save in the direst emergency, since you wish to take me a living prisoner—I would find it most distressing to have to carry for the rest of my life a flaw on my body. So, may I request you to withdraw your ray-guns with two fingertips and put them on the floor? Observe—your fingertips. Will you be so kind?"

The Hawk looked at him for a minute. Then silently he obeyed. He knew that the Eurasian would have no compunctions about shooting him down in cold blood; but, on the other hand, even as the man had said, he could not kill Ku Sui, but had to capture him, in order to take him to Earth to confess to crimes now blamed on Eliot Leithgow. "Do as he says, Friday," he instructed the still staring negro; and, like a man in a trance, Friday obeyed.

"Thank you," the Eurasian said. "It was a most friendly thing to do." He paused. "I suppose you are wondering how I arrived here, and why you did not see me come. Well, I shall certainly tell you, in return for your favor. But first—ah, friend Carse—your gesture! A reminder, I assume."

Slowly the Hawk was stroking the bangs of hair which had been trained to obscure his forehead. There was no emotion on his chilly face as he answered, no slightest sign of feeling unless it were a slight trembling of the left eyelid—significant enough to those who could read it.

"Yes," he whispered, "a reminder. I do not like to wear my hair like this, Ku Sui, and I want you to know that I've not forgotten; that, though I'm now in your power, there'll be a day——"

"But you wouldn't threaten your host!" the other said with mock surprise. "And surely you wouldn't threaten me, of all men.