So, his gray eyes reflective, he strode to the Scorpion's radio panel and a moment later was saying over and over in a toneless voice:

"XX-1 calling XX-2—XX-1 calling XX-2—XX-1 calling XX-2...."

After a full two minutes there was still no answer from the loudspeaker. He kept calling: "XX-1 calling XX-2—XX-1 calling XX-2—XX-1 calling——"

He broke off as words in English came softly from the loudspeaker:

"XX-2 answering XX-1. Do you hear me?"

"Yes. Give me protected connection. Highly important no outsider overhears."

"All right," the gentle voice answered. "Protected. Go ahead, old man."

The Hawk relaxed and his face softened. "How are you, Eliot?" he asked almost tenderly.

"Just fine, Carse," came in the clear, cultured voice of Master Scientist Eliot Leithgow, probably the greatest scientific mind in the solar system, Ku Sui being the only possible exception. He spoke now from his secret laboratory on Jupiter's Satellite III, near Porno, this transcendent genius who, with Friday, was one of Carse's two trusted comrades-in-arms. "I've been expecting you," he went on. "Has something happened?"

"I'm concerned with Ku Sui again," the Hawk told him swiftly. "Please excuse me; I have to be brief. I can't take any chances of his hearing any of this." He related the events of the last two days: Judd's attack on the Iapetus ranch, the subsequent fight and outcome, and finally his present position and intention of keeping the rendezvous. "The odds are pretty heavily against me, M. S.," he went on. "It would be stupid not to admit that I may not come out of this affair alive—and that's why I'm calling. My affairs, of course, are in your hands. You know where my storerooms and papers are. Sell my trading posts and ranches; Hartz of Newark-on-Venus is the best man to deal through. But I'd advise you to keep for yourself that information on the Pool of Radium. Look into it sometime. I'm in Judd's ship, the Scorpion; our Star Devil's on Iapetus, hidden in the jungle near the ranch. That's all, I think."

"Carse, I should be with you!"

"No, M. S.—couldn't risk it. You're too valuable a man. But don't worry, you know my luck. I'll very likely be down to see you after this meeting, and perhaps with a visitor who will enable you once again to return to an honorable position on Earth. Where will you be?"

"In eight Earth days? Let's make it Porno, at the house you know. I'll come in for some supplies and wait for you."

"Good," the Hawk said shortly. "Good-by, M. S."

He paused, his hand on the switch. There came a parting wish:

"Good luck, old fellow. Get him! Get him!"

The Master Scientist's voice trembled at the end. Through Ku Sui he had lost honor, position, home—all good things a man on Earth may have; through Ku Sui he, the gentlest of men, was regarded by Earthlings as a black murderer and there was a price on his head. Hawk Carse did not miss the trembling in his voice. As he switched off, the adventurer's eyes went bleak as the loneliest deeps of space....

¹ See the November, 1931, issue of Astounding Stories.

CHAPTER II

The Coming of Ku Sui

Straight through the vast cold reaches that stretched between one mighty planet and another the Scorpion arrowed, Carse and Friday standing watch and watch, Sako always on duty with the latter. Behind, Saturn's rings melted smaller, and ahead a dusky speck grew against the vault of space until the red belts and one great seething crimson spot that marked it as Jupiter stood out plainly. By degrees, then, the ship's course was altered as Carse checked his calculations and made minor corrections in speed and direction. So they neared the rendezvous. And a puzzled furrow grew on Friday's brow.

What was bothering his master? Instead of becoming more impassive and coldly emotionless as the distance shortened, he showed distinct signs of worry. This might be natural in most men, but it was unusual in the Hawk. Often the negro found him abstractedly smoothing his bangs of hair, pacing the length of the control cabin, glancing, plainly worried, at the visi-screen. What special thing was wrong? Friday wondered again and again—and then, in a flash, he knew.

"Why—how we goin' to see Dr. Ku?" he burst out. "Didn't that Judd say somethin'——"

The Hawk nodded. "That's just the problem, Eclipse. For you'll remember Judd said that Ku Sui 'comes out of darkness, out of empty space.' That might mean invisibility or the Fourth Dimension—and God help us if he's solved the problem of dimensional traveling. I don't know—but it's something I can't well prepare against." He fell to musing again, utterly lost in thought.

A day and a half later found Friday genuinely worried—an unusual state for the always cheerful black. The laugh wrinkles of his face were re-twisted into lines of anxiety which gave his face a most solemn and lugubrious expression. From time to time he grasped the butt of his ray-gun with a grip that would have pulped an orange; occasionally his rolling brown eyes sought the gray ones of the Hawk, only to return as by a magnet to the visi-screen, whose five adjoining squares mirrored the whole sweep of space around them.

Jupiter now filled one side of the forward observation window. It was a vast, red-belted disk, an eye-thrilling spectacle at their distance, roughly a million miles. Against it were poised two small pale globes, the larger of which was Satellite III. Several hours before, when they had been closer to the satellite, Carse had scrutinized it through the electelscope and made out above its surface a silver dot which was a space-ship. It was bound inward toward Port o' Porno, and might well have been one of Ku Sui's. But the Scorpion, slowing down for her rendezvous, had attracted no attention and had passed undisturbed.

Now she hung motionless—that is, motionless with respect to the sun. Only the whisper of the air-renewing machinery disturbed the tension in her control cabin where the three men stood waiting, glancing back and forth from the visi-screen to the Earth clock and its calendar attachment. The date the clock showed was 24 January, the time, 10:21 P. M. Dr. Ku Sui was one minute late.

Sako, the captive, was sullen and restless, and made furtive glances at the Hawk, who stood detached, arms hanging carelessly at his sides, gray eyes half closed, giving in his attitude no hint of the strain the others were feeling. But his attitude of being relaxed and off his guard was deceptive—as Sako found out. Suddenly his left hand seemed to disappear; there was a hiss, an arrowing streak of spitting orange light; and Sako was gaping foolishly at the arm he had stealthily raised to one of the radio switches. A smoking sear had appeared as if by magic across it.

Hawk Carse sheathed his gun. "I would advise you to try no more obvious tricks," he said coldly. "Cutting in our microphone is too simple a way to give warning to Dr. Ku Sui. Move away from there. And don't forget your lines when Dr. Ku calls. You will never act a part before a more critical and deadly audience."

Sako mumbled something and rubbed his arm. A pitying smile came to Friday's face as he comprehended what had happened. "You damned fool!" he said.

It was 10:22 P.M. Still, in the visi-screen, no other ship. Nothing but the giant planet, the smaller satellites poised against it, and the deep star-spangled curtain of black space all