moment later a thing of metal and fabric, fitted with drills and delicate thread-like tentacles, and formed like a giant Sadu moth of Mars, darted out from behind a curtain where it had been hiding. It flew up through the air-tube which had been its means of entrance to the room. On the roof it met a black nightmare, and by means of signs traced in the air with an intelligence that was paradoxically human, it directed the monster to Shelby's apartment below.

The first sensation which bore itself in upon Shelby's consciousness when he was regaining his senses was a terrific throbbing pain in his head. He opened his rheum-plastered eyelids and looked about him. He was lying in a bunk within a small dim-lit compartment. Polished duralumin walls gleamed all about. At the center of his prison was a table, and beyond, built into the opposite wall, was another bunk. There was a black blob of something sprawling on the mattress, but he could not see clearly what it was. The illumination globe in the ceiling was not burning, and only a faint glow filtered through the curtained, circular window. A muffled purring vibration told Shelby that he was aboard a speeding space ship.

Aroused evidently by the stirring of its charge, the thing in the opposite berth arose and strode leisurely toward the Earthian. The metal of its harness tinkled, and sharp points of light flashed against its ebony body, like gems sewn into a sable curtain that is being swayed by a vagrant draft of air.

The Earthman recognized the creature immediately as his recent pursuer. It had pressed the light switch now, and the illumination globe glowed softly. Then the thing bent over Shelby, and with a gentleness that was surprising, it rolled him over and examined his bandaged wound briefly.

The young man conquered his revulsion sufficiently to look up into the monster's face. He thought that it was odd that the sight of it did not terrify him. No, really it was not more hideous than the visages of insects he had seen through a microscope. He studied the hard chitinous visors that blinked over the monster's eyes—the hollow where its nose should have been; and he searched for some hint that there was a human personality within that knotted carcass but found none. The lipless mouth and the blankly staring eyes were without any expression that he could interpret.

Two things struck Shelby as being peculiar—the fact that the monster did not seem to breathe, and the icy coldness of its hands.

The thing walked to the door, unlocked it, and left the room. The engineer heard a grating of the key being turned when the door had been shut.

Taking advantage of the opportunity to move about without being observed, he jumped out of bed and hurried to the window. It was then that he noticed that there was a metal band about his right ankle. A long light chain led from it to an eyelet in the wall. Truly he was a prisoner!

A single glance through the porthole confirmed what he had known was true—the black sky and the unwinking stars of space.

There was a narrow walk beneath the window, running the full length of the flier's hull. The railing of woven wire cast a checkered shadow on the walk. Somewhere toward the stern a blazing sun was shining, but Shelby could not see it.

His first thoughts concerned some means of spoiling the plans of Selba's band. He guessed, of course, that they were responsible for his present position, and he realized that it was likely that the zero hour of their attack upon the planets was not far off. Could he escape?—a practical impossibility.

Nevertheless he looked longingly at the emergency space-boat hugging close to the hull of its mother ship, and fitted so admirably into her streamlining. If he could get to the entrance of that boat—it was in some other room farther toward the bow—he could give his captors a run for their money and perhaps reach Earth. And if he did? Shelby had great confidence in the Atomic Ray. He removed the top from the button where he had secreted the pink crystal. It was still there.

But how could he get into the space-boat? Plainly it could not be accomplished now. Perhaps soon—in a few hours maybe, an opportunity would present itself. And there were other things he might do. A moment in the engine room, and he could blow the ship to atoms, and with it, most of the ringleaders of the Selba crowd. Stoically Shelby realized that he too would be destroyed, but if he could serve his world, he would not hesitate to make the move.

Bent on getting as well acquainted with his present environment as he could, the Earthman proceeded to examine minutely everything that was within the range of his senses. He tested the strength of his chain, and began to fumble over each link, without having any definite idea of what value the knowledge gleaned from such a procedure would be to him.

He had reached about the tenth link when he heard a sound above the purr of rocket motors—voices. There were two of them. One was a man's; the other was soft and feminine. Shelby knew it at once—Janice Darell's! So she too was aboard the space flier! He realized it with a pang of apprehension. In vain the Earthman tried to catch the words they were saying, but beyond detecting the chilly tone in the girl's voice, he could get no idea of what they were talking about. Apparently they were in the room next to his.

He heard footsteps in the hall outside, and returned quickly to his bunk. Three people entered the room. The first was the black monster. Shelby gave a gasp when he saw who followed it—Jan. She looked tired and worn but in her face there was no hint of fear. She smiled wanly at Shelby. There was another behind her. It was Hekalu Selba—the man the Earthian thought he had killed! For once Shelby was really dumbfounded. He uttered the Martian's name without thinking.

The noble grinned in Satanic amusement. "It is I, none other, my friend," he said. "Aren't you glad to see me? You look as though you were being visited by a ghost."

The Martian chuckled. "But thanks to a breast armor I still belong to this plane of existence. I admit though that you gave me a great scare when you nearly, but not quite, escaped. My four bombing fliers supplied an adequate diversion for the Municipal Patrol, didn't they? And my Sadu moth, radio controlled automaton—it functioned perfectly!"

Shelby rose from the bunk and sauntered toward his captor. Hekalu made no move to stop him. "Now that you have Miss Darell and me nicely trapped, what do you intend to do?" Shelby inquired coldly.

The Martian laughed. "You have a very inquisitive nature, Mr. Shelby," he said. "What do you expect me to do? Continue with my plans which you so almost successfully spoiled, my friend." Here Hekki's voice became suddenly excited and husky; his lips curled and his eyes took on the fanatical look of a megalomaniac who sees within his grasp his dream of power.

"Very soon," he lisped, "we strike. Mars first, then your planet. I shall be great—greater than all the combined rulers of the millenniums gone by, and Janice here, will share my greatness." The slender arm of Selba stole around the waist of the girl beside him. She did not try to draw away. "That last little idea maddens you, doesn't it, Mr. Shelby?" he added with a sneer.

Shelby felt a flush of heat in his cheeks. What happened to Jan that she should permit the noble to be so familiar with her? Had she been dazzled by his wealth and his promises of what stupendous things the future would bring? For a fraction of a second something seemed to let go in the Earthman's mind, and then he saw the fleeting look in the girl's eyes. He checked the impulse that had urged him to send a fist crashing into the face of the smirking noble. Certainly such an act of violence could accomplish no good.

Shelby looked at the black monster. It was standing beside the table, and leaned forward, so that its knuckles rested ape-like upon the floor. It was gazing