occasionally to reveal the single flaming eye and massive iron jaws each contained. There were riveted joints and levers, wheels and gears that moved as the creatures moved; darting lights that flashed forth from trunnion-mounted cases like the searchlights of a battleship of Earth; great swiveled arms with grappling hooks attached. They were mechanical contrivances—the metal monsters of which the Wanderer had spoken. Whether their brains were comprised of active living cells or whether they were cold, calculating machines of metallic parts, Bert was never to know.

"See, the gateway," the Wanderer was saying. "They are investigating. It is the beginning of the end of Urtraria—all as it occurred in the dim and distant past."

He gripped Bert's arm, pointing a trembling finger, and his face was a terrible thing to see in the eery light of their sphere.

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 encompassed 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 space, 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 snatched 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 space 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 space, 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 repetition 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 pass—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