"I don't know," he replied, "but we'll find out a little later. I am relieved to find them here, and I doubt if they are harmed."

The sketch which he was making was one of the solar system, and, when he had finished, he marked the earth with a cross and handed the notebook to one of the beetles. The insect took it and showed it to his companions; so far as I was able to judge expressions, they were amazed to find that we had knowledge of the heavenly bodies. The beetle took Jim's pencil in one of its hands and, after examining it carefully, made a cross on the circle which Jim had drawn to represent the planet Mercury.

"They come from Mercury," exclaimed Jim in surprise as he showed me the sketch. "That accounts for a good many things; why they are so lethargic, for one thing. Mercury is much smaller than the earth and the gravity is much less. According to Mercurian standards, they must weigh a ton each. It is quite a tribute to their muscular development that they can move and support their weight against our gravity. They can understand a drawing all right, so we have a means of communicating with them, although a pretty slow one and dependent entirely on my limited skill as a cartoonist. I wonder if we are free to move about?"

"The only way to find out is to try," I replied and stood erect. The beetles offered no objection and Jim stood up beside me. We walked, or rather edged, our way toward the side of the ship. The insects watched us when we started to move and then evidently decided that we were harmless. They turned from us to the working of the ship. One of them manipulated some dials on the instrument board. One of the rods which held our flyer released its grip, came in toward the Mercurian ship and coiled itself up on the floor, or the place where the floor should have been. The insect touched another dial. Jim threw caution to the winds, raced across the floor and grasped the beetle by the arm.

The insect looked at him questioningly; Jim produced the notebook and drew a sketch representing our flyer falling. On the level be had used to represent the ground he made another sketch of it lying in ruins. The beetle nodded comprehendingly and turned to another dial; the ship sank slowly toward the ground.

We sank until we hung only a few feet from the ground when our flyer was gently lowered down. When it rested on the ground, the wire which had held it uncoiled, came aboard and coiled itself up beside the others. As the Mercurian ship rose I noticed idly that the door which had been torn from our ship and dropped lay within a few yards of the ship itself. The Mercurian ship rose to an elevation of a hundred feet, drifting gently over the city.

As we rose I determined to try the effect of my personality on the beetles. I approached the one who seemed to be the leader and, putting on the most woeful expression I could muster, I looked at the floor. He did not understand me and I pretended that I was falling and grasped at him. This time he nodded and stepped to the instrument board. In a moment the floor became visible. I thanked him as best I could in pantomime and approached the walls. They were so transparent that I felt an involuntary shrinking as I approached them. I edged my way cautiously forward until my outstretched hand encountered a solid substance. I looked out.

At the slow speed we were traveling the drone of our motors was hardly audible to us, and I felt sure that it could not be heard on the ground.

Once their curiosity was satisfied, our captors paid little or no attention to me and left me free to come and go as I wished. I made my way cautiously toward the children, but ran into a solid wall.

Remembering Jim's words, I made my way back toward him without displaying any interest.

Jim could probably have wandered around as I did had he wished, but he chose to occupy his time differently. With his notebook and pencil he carried on an extensive conversation, if that term can be applied to a crudely executed set of drawings, with the leader of the beetles. I was not especially familiar with the methods of control of s.p.a.ce ships and I could make nothing of the maze of dials and switches on the instrument board.

For half an hour we drifted slowly along. Presently one of the beetles approached, seized my arm and turned me about. With one of his arms he pointed ahead. A mile away I could see another s.p.a.ce flyer similar to the one we were on.

"Here comes another one, Jim." I called.

"Yes, I saw it some time ago. I don't know where the third one is."

"Are there three of them?"

"Yes. Three of them came here yesterday and are exploring the country round about here. They are scouts sent out from the fleet of our brother planet to see if the road was clear and what the world was like. They spotted the hole through the layer with their telescope and sent their fleet out to pay us a visit. He tells me that the scouts have reported favorably and that the whole fleet, several thousand ships, as near as I can make out, are expected here this evening."

"Have you solved the secret of their invisibility?"

"Partly. It is as I expected. The walls of the ship are double, the inner one of metal and the outer one of vitrolene or some similar perfectly transparent substance. The s.p.a.ce between the walls is filled with some substance which will bend both visible and ultra-violet rays along a path around the ship and then lets them go in their original direction. The reason why we can see through the walls and see the protective coating of that ship coming is that they are generating some sort of a ray here which acts as a carrier for the visible light rays. I don't know what sort of a ray it is, but when I get a good look at their generators, I may be able to tell. Are you beginning to itch and burn?"

"Yes, I believe that I am, although I hadn't noticed it until you spoke."

"I have been noticing it for some time. From its effects on the skin, I am inclined to believe it to be a ray of very short wave-length, possibly something like our X-ray, or even shorter."

"Have you found out what they intend to do with us?"

"I don't think they have decided yet. Possibly they are going to take us up to the leader of their fleet and let him decide. The cuss that is in command of this ship seems surprised to death to find out that I can comprehend the principles of his ship. He seems to think that I am a sort of a rara avis, a freak of nature. He intimated that he would recommend that we be used for vivisection."

"Good Lord!"

"It's not much more worse than the fate they design for the rest of their captives, at that."

"What is that?"

"It's a long story that I'll have to tell you later. I want to watch this meeting."

The other ship had approached to within a few yards and floated stationary, while some sort of communication was exchanged between the two. I could not fathom the method used, but the commander of our craft clamped what looked like a pair of headphones against his body and plugged the end of a wire leading from them into his instrument board.

From time to time various colored lights glowed on the board before him. After a time he uncoupled his device from the board, and one of the long rods shot out from our ship to the other. It returned in a moment clamped around the body of a young girl. As the came on board, she was lowered onto the deck beside the other children. Like them, she was stiff and motionless. I gave an exclamation and sprang forward.

"Pete!"

Jim's voice recalled me to myself, and I watched the child laid with the others with as disinterested an expression as I could muster. I had never made a mistake in following Jim Carpenter's lead and I knew that somewhere in his head a plan was maturing which might offer us some chance of escape.

Our ship moved ahead down a long slant, gradually dropping nearer to the ground. I watched the maneuver with interest while Jim, with his friend the beetle commander, went over the ship. The insect was evidently amused at Jim and was determined to find out the limits of his intelligence, for he pointed out various controls and motors of the ship and made elaborate sketches which Jim seemed to comprehend fairly well.

One of the beetles approached the control board and motioned me back. I stepped away from the board; evidently a port in the side of the vessel opened, for I felt a breath of air and could hear the hum of the city. I walked to the side and glanced down, and found that we were floating about twenty feet off the ground over a street on the edge of the city.

On the street a short distance ahead of us two children, evidently returning from school, to judge by the books under their arms, were walking unsuspectingly along. A turn of the dial sped up our motors, and as the hum rang out in a louder key the children looked upward. Two of the long flexible wires shot out and wrapped themselves about the children; screaming, they were lifted into the s.p.a.ce flyer. The port through which they came in shut with a clang and the ship rose rapidly into the air. The children were released from the wires which coiled themselves up on deck and the beetle who had operated them stepped forward and grasped the nearer of the children, a boy of about eleven, by the arm. He raised the boy, who was paralyzed with terror, up toward his head and gazed steadily into his eyes. Slowly the boy ceased struggling and became white and rigid. The beetle laid him on the deck and turned to the girl. Involuntarily I gave a shout and sprang forward, but Jim grasped me by the arm.

"Keep quiet, you darned fool!" he cried. "We can do nothing now. Wait for a chance!"

"We can't stand here and see murder done!" I protested.

"It's not murder. Pete, those children aren't being hurt. They are being hypnotized so that they can be transported to Mercury."

"Why are they taking them to Mercury?" I demanded.

"As nearly as I can make out, there is a race of men up there who are subject to these beetles. This ship is radium propelled, and the men and women are the slaves who work in the radium mines. Of course the workers soon become s.e.xless, but others are kept for breeding purposes to keep the race alive. Through generations of in-breeding, the stock is about played out and are getting too weak to be of much value.

"The Mercurians have been studying the whole universe to find a race which will serve their purpose and they have chosen us to be the victims. When their fleet gets here, they plan to capture thousands of selected children and carry them to Mercury in order to infuse their blood into the decadent race of slaves they have. Those who are not suitable for breeding when they grow up will die as slaves in the radium mines."

"Horrible!" I gasped. "Why are they taking children, Jim? Wouldn't adults suit their purpose better?"

"They are afraid to take adults. On Mercury an earthman would have muscles of unheard of power and adults would constantly strive to rise against their masters. By getting children, they hope to raise them to know nothing else than a life of slavery and get the advantage of their strength without risk. It is a clever scheme."

"And are we to stand here and let them do it?"

"Not on your life, but we had better hold easy for a while. If I can get a few minutes more with that brute I'll know enough about running this ship that we can afford to do away with them. You have a pistol, haven't you?"

"No."

"The devil! I thought you had. I have an automatic, but it only carries eight sh.e.l.ls. There are eleven of these insects and unless we can get the jump on them, they'll do us. I saw what looks like a knife lying near the instrument board; get over near it and get ready to grab it as soon as you hear my pistol. These things are deaf and if I work it right I may be able to do several of them in before they know what's happening. When you attack, don't try to ram them in the back; their backplates are an inch thick and will be proof against a knife thrust.

Aim at their eyes; if you can blind them, they'll be helpless. Do you understand?"