A sharply outlined circle of blue-white appeared down there in the midst of the squirming monsters. The sphere drifted lower and Bert was able to see that a complicated machine was being trundled out from an arched doorway in the base of one of the conical dwellings. It was moved to the edge of the light circle which was the bowl on that rooftop of Urtraria. The same bowl! A force area like that used by Tom Parker, an area existent in many planes of the fifth dimension simultaneously, an area where the various components of wave motion merged and became as one. The gateway between planes!

The machine of the metal monsters was provided with a huge lens and a reflector, and these were trained on the bowl. Wheels and levers of the machine moved swiftly. There came an orange light from within that was focused upon lens and reflector to strike down and mingle with the cold light of the bowl. A startling transformation ensued, for the entire area within view was encompa.s.sed with a milky diffused brightness in which two worlds seemed to intermingle and fuse. There were the rooftops of the city in Urtraria and its magnificent domes, a transparent yet substantial reality superimposed upon the gloomy city of cones of the metal monsters.

"Jupiter!" Bert breathed. "They're going through!"

"They are, Earthling. More accurately, they did--thousands of them; millions." Even as the Wanderer spoke, the metal monsters were wriggling through between the two planes, their enormous bodies moving with menacing deliberation.

On the rooftops back in Urtraria could be seen the frantic, fleeing forms of humanlike beings--the Wanderer's people.

There was a sharp click from the control panel and the scene was blotted out by the familiar maze of geometric shapes, the whirling, dancing light-forms that rushed madly past over the vast arch which spanned infinity.

"Where were you at the time?" asked Bert. Awed by what he had seen and with pity in his heart for the man who had unwittingly let loose the horde of metal monsters on his own loved ones and his own land, he stared at the Wanderer.

The big man was standing with face averted, hands clutching the rail of the control panel desperately. "I?" he whispered. "I was roaming the planes, exploring, experimenting, immersed in the pursuits that went with my insatiable thirst for scientific data and the broadening of my knowledge of this complex universe of ours. Forgetting my responsibilities. Unknowing, unsuspecting."

"You returned--to your home?"

"Too late I returned. You shall see; we return now by the same route I then followed."

"No!" Bert shouted, suddenly panicky at thought of what might be happening to Joan and Tom in the land of the Bardeks. "No, Wanderer--tell me, but don't show me. I can imagine. Seeing those loathsome big worms of iron and steel, I can well visualize what they did. Come now, have a heart, man; take me to my friends before...."

"Ah-h!" The Wanderer looked up and a benign look came to take the place of the pain and horror which had contorted his features. "It is well, O Man-Called-Bert. I shall do as you request, for I now see that my mission has been well accomplished. We go to your friends, and fear you not that we shall arrive too late."

"Your--your mission?" Bert calmed immediately under the spell of the Wanderer's new mood.

"My mission throughout eternity, Earthling--can't you sense it?

Forever and ever I shall roam infra-dimensional s.p.a.ce, watching and waiting for evidence that a similar catastrophe might be visited on another land where warm-blooded thinking humans of similar mold to my own may be living out their short lives of happiness or near-happiness. Never again shall so great a calamity come to mankind anywhere if it be within the Wanderer's power to prevent it. And that is why I s.n.a.t.c.hed you up from your friend's laboratory. That is why I have shown to you the--"

"Me, why me?" Bert exclaimed.

"Attend, O Earthling, and you shall hear."

The mysterious intangibilities of the cosmos whirled by unheeded by either as the Wanderer's tale unfolded.

"When I returned," he said, "the gateway was closed forever. I could not reenter my own plane of existence. The metal monsters had taken possession; they had found a better and richer land than their own, and when they had completed their migration they destroyed the generator of my force area. They had shut me out; but I could visit Urtraria--as an outsider, as a wraith--and I saw what they had done. I saw the desolation and the blackness of my once fair land. I saw that--that none of my own kind remained. All, all were gone.

"For a time my reason deserted me and I roamed infra-dimensional s.p.a.ce a madman, self-condemned to the outer realms where there is no real material existence, no human companionship, no love, no comfort. When reason returned, I set myself to the task of visiting other planes where beings of my own kind might be found and I soon learned that it was impossible to do this in the body. To these people I was a ghostly visitant, if they sensed my presence at all, for my roamings between planes had altered the characteristics of atomic structure of my being. I could no longer adapt myself to material existence in these planes of the fifth dimension. The orbits of electrons in the atoms comprising my substance had become fixed in a new and outcast oscillation interval. I had remained away too long. I was an outcast, a wanderer--the Wanderer of Infinity."

There was silence in the sphere for a s.p.a.ce, save only for the gentle whirring of the motors. Then the Wanderer continued:

"Nevertheless, I roamed these planes as a nonexistent visitor in so far as their peoples were concerned. I learned their languages and came to think of them as my own, and I found that many of their scientific workers were experimenting along lines similar to those which had brought disaster to Urtraria. I swore a mighty oath to spend my lifetime in warning them, in warding off a repet.i.tion of so terrible a mistake as I had made. On several occasions I have succeeded.

"And then I found that my lifetime was to be for all eternity. In the outer realms time stands still, as I have told you, and in the plane of existence which was now mine--an extra-material plane--I had no prospect of aging or of death. My vow, therefore, is for so long as our universe may endure instead of for merely a lifetime. For this I am duly thankful, for I shall miss nothing until the end of time.

"I visited planes where other monsters, as clever and as vicious as the metal ones who devastated Urtraria, were bending every effort of their sciences toward obtaining actual contact with other planes of the fifth dimension. And I learned that such contact was utterly impossible of attainment without a gateway in the realm to which they wished to pa.s.s--a gateway such as I had provided for the metal monsters and such as that which your friend Tom Parker has provided for the Bardeks, or spider men, as you term them.

"In intra-dimensional s.p.a.ce I saw the glow of Tom Parker's force area and I made my way to your world quickly. But Tom could not get my warning: he was too stubbornly and deeply engrossed in the work he was engaged in. The girl Joan was slightly more susceptible, and I believe she was beginning to sense my telepathic messages when she sent for you. Still and all, I had begun to give up hope when you came on the scene. I took you away just as the spider men succeeded in capturing your friends, and now my hope has revived. I feel sure that my warning shall not have been in vain."

"But," objected Bert, "you've warned _me_, not the scientist of my world who is able to prevent the thing--"

"Yes, _you_," the Wanderer broke in. "It is better so. This Tom Parker is a zealot even as was I--a man of science thinking only of his own discoveries. I am not sure he would discontinue his experiments even were he to receive my warning in all its horrible details. But you, O Man-Called-Bert, through your love of his sister and by your influence over him, will be able to do what I can not do myself: bring about the destruction of this apparatus of his; impress upon him the grave necessity of discontinuing his investigations. You can do it, and you alone, now that you fully understand."

"Sa-ay! You're putting it up to me entirely?"

"Nearly so, and there is no alternative. I believe I have not misjudged you; you will not fail, of that I am certain. For the sake of your own kind, for the love of Joan Parker--you will not fail. And for me--for this small measure of atonement it is permitted that I make or help to make possible--"

"No, I'll not fail. Take me to them, quick." Bert grinned understandingly as the Wanderer straightened his broad shoulders and extended his hand.

There was no lack of substantiality in the mighty grip of those closing fingers.

Again the sphere's invisible motors increased speed, and again the dizzying kaleidoscope of color swept past them more furiously.

"We will now overtake them--your friends," said the Wanderer, "in the very act of pa.s.sing between planes."

"Overtake them...." Bert mumbled. "I don't get it at all, this time traveling. It's over my head a mile."

"It isn't time travel really," explained the Wanderer. "We are merely closing up the time-s.p.a.ce interval, moving to the precise spot in the universe where your friend's laboratory existed at the moment of contact between planes with your world and that of the Bardeks. We shall reach there a few seconds after the actual capture."

"No chance of missing?" Bert watched the Wanderer as he consulted his mathematical data and made new adjustments of the controls.

"Not the slightest; it is calculated to a nicety. We could, if we wished, stop just short of the exact time and would see the re-occurrence of their capture. But only as unseen observers--you can not enter the plane as a material being during your own actual past, for your ent.i.ty would then be duplicated. Of course, I can not enter in any case. But, moving on to the instant after the event, as we shall do, you may enter either plane as a material being or move between the two planes at will by means of the gateway provided by Tom Parker's force area. Do you not now understand the manner in which you will be enabled to carry out the required procedure?"

"H-hmm!" Bert wasn't sure at all. "But this moving through time," he asked helplessly, "and the change from one plane of oscillation to another--they're all mixed up--what have they to do with each other?"

"All five dimensions of our universe are definitely interrelated and dependent one upon the other for the existence of matter in any form whatsoever. You see--but here we are."

The motors slowed down and a t.i.tanic page seemed to turn over in the cosmos with a vanishing blaze of magnificence. Directly beneath them glowed the disk of blue-white light that was Tom's force area. The sphere swooped down within its influence and came to rest.

"Make haste," the Wanderer said. "I shall be here in the gateway though you see me not. Bring them here, speedily."

On the one side Bert saw familiar objects in Tom's laboratory, on the other side the white cliff and the pitchy sea of the Bardek realm. And the cage of basket-weave between, with his friends inside struggling with the spider men. It was the instant after the capture.

"Joan! Tom!" Bert shouted.

A side of the sphere had opened and he plunged through and into the Bardek plane--to the inky surface of the sea, fully expecting to sink in its forbidding depths. But the stuff was an elastic solid, springy under his feet and bearing him up as would an air-inflated cushion. He threw himself upon the cage and tore at it with his fingers.

The whimpering screams of the spider men were in his ears, and he saw from the corner of his eye that other of the tortoiselike mounds were rising up out of the viscid black depths, dozens of them, and that hundreds of the Bardeks were closing in on him from all directions.

Weapons were in their hands, and a huge engine of warfare like a caterpillar tractor was skimming over the sea from the cliff wall with a great grinding and clanking of its mechanisms.