There had been a queer quivering when rifles and pack had touched the upthrust of rock. Then they had seemed to melt into it.

“I’d say they dropped into the lake,” said Jim.

“There’s no lake. They dropped into some break in the rock. Come in-”

He gripped my shoulder.

“Wait, Leif. Go slow.”

I followed his pointing finger. The barrier of stones had vanished. Where they had been, the slide ran, a smooth tongue of stone, far out into the valley.

“Come on,” I said.

We went down, testing every step. With each halt, the nibbled plain became flatter and flatter, the boulders squatted lower and lower. A cloud drifted over the sun. There were no boulders. The valley floor stretched below us, a level slate-grey waste!

The slide ended abruptly at the edge of this waste. The rocks ended as abruptly, about fifty feet ahead. They stood at the edge with the queer effect of stones set in place when the edge had been viscous. Nor did the waste appear solid; it, too, gave the impression of viscosity; through it ran a slight but constant tremor, like waves of heat over a sun-baked road — yet with every step downward the bitter, still cold increased until it was scarcely to be borne.

There was a narrow passage between the shattered rocks and the cliff at our right. We crept through it. We stood upon an immense flat stone at the very edge of the strange plain. It was neither water nor rock; more than anything, it had the appearance of a thin opaque liquid glass, or a gas that had been turned semi-liquid.

I stretched myself out on the slab, and reached out to touch it. I did touch it — there was no resistance; I felt nothing. I let my hand sink slowly in. I saw my hand for a moment as though reflected in a distorting mirror, and then I could not see it at all. But it was pleasantly warm down there where my hand had disappeared. The chilled blood began to tingle in my numbed fingers. I leaned far over the stone and plunged both arms in almost to the shoulders. It felt damned good.

Jim dropped beside me and thrust in his arms.

“It’s air,” he said.

“Feels like it —” I began, and then a sudden realization came to me —“the rifles and the pack! If we don’t get them we’re out of luck!”

He said: “If Khalk’ru is — guns aren’t going to get us away from him.”

“You think this —” I stopped, memory of the shadowy shape in the lake of illusion coming back to me.

“Usunhi’yi, the Darkening-land. The Shadowed-land your old priest called it, didn’t he? I’d say this fits either description.”

I lay quiet; no matter what the certainty of a coming ordeal a man may carry in his soul, he can’t help a certain shrinking when he knows his foot is at the threshold of it. And now quite clearly and certainly I knew just that. All the long trail between Khalk’ru’s Gobi temple and this place of mirage was wiped out. I was stepping from that focus of Khalk’ru’s power into this one — where what had been begun in the Gobi must be ended. The old haunting horror began to creep over me. I fought it.

I would take up the challenge. Nothing on earth could stop me now from going on. And with that determination, I felt the horror sullenly retreat, leave me. For the first time in years I was wholly free of it.

“I’m going to see what’s down there.” Jim drew up his arms. “Hold on to my feet, Leif, and I’ll slip over the edge of the stone. I felt along its edge and it seems to go on a bit further.”

“I’ll go first.” I said. “After all, it’s my party.”

“And a fine chance I’d have to pull you up if you fell over, you human elephant. Here goes — catch hold.”

I had just time to grip his ankles as he wriggled over the stone, and his head and shoulders passed from sight. On he went, slowly writhing along the slanting rock until my hands and arms were hidden to the shoulders. He paused — and then from the mysterious opacity in which he had vanished came a roar of crazy laughter.

I felt him twist and try to jerk his feet away from me. I pulled him, fighting against me every inch of the way, out upon the stone. He came out roaring that same mad laughter. His face was red, and his eyes were shining drunkenly; he had in fact all the symptoms of a laughing drunk. But the rapidity of his respiration told me what had happened.

“Breathe slowly,” I shouted in his ear. “Breathe slowly, I tell you.”

And then, as his laughter continued and his struggles to tear loose did not abate, I held him down with one arm and dosed his nose and mouth with my hand. In a moment or two he relaxed. I released him; and he sat up groggily.

“Funniest things,” he said, thickly. “Saw funniest faces . . . .”

He shook his head, took a deep breath or two, and lay back on the stone.

“What the hell happened to me, Leif?”

“You had an oxygen bun, Indian,” I said. “A nice cheap jag on air loaded with carbon-dioxide. And that explains a lot of things about this place. You came up breathing three to the second, which is what carbon-dioxide does to you. Works on the respiratory centres of the brain and speeds up respiration. You took in more oxygen than you could use, and you got drunk on it. What did you see before the world became so funny?”

“I saw you,” he said. “And the sky. It was like looking up out of water. I looked down and around. A little below me was something like a floor of pale green mist. I couldn’t see through it. It’s warm in there, good and plenty warm, and it smells like trees and flowers. That’s all I managed to grasp before I went goofy. Oh, yes, this rock fall keeps right on going down. Maybe we can get to the bottom of it — if we don’t laugh ourselves off. I’m going right out and sit in that mirage up to my neck — my God, Leif, I’m freezing!”

I looked at him with concern. His lips were blue, his teeth chattering. The transition from the warmth to the bitter cold was having its effect, and a dangerous one.

“All right,” I said, rising. “I’ll go first. Breathe slowly, take deep, long breaths as slowly as you can, and breathe out just as slowly. You’ll soon get used to it. Come on.”

I slung the remaining pack over my back, craw-fished over the side of the stone, felt solid rock under my feet, and drew myself down within the mirage.

It was warm enough; almost as warm as the steam-room of a Turkish bath. I looked up and saw the sky above me like a circle of blue, misty at its edges. Then I saw Jim’s legs dropping down toward me, his body bent back from them at an impossible angle. I was seeing him, in fact, about as a fish does an angler wading in its pool. His body seemed to telescope and he was squatting beside me.

“God, but this feels good!”

“Don’t talk,” I told him. “Just sit here and practise that slow breathing. Watch me.”

We sat there, silently, for all of half an hour. No sound broke the stillness around us. It smelled of the jungle, of fast growing vigorous green life, and green life falling as swiftly into decay; and there were elusive, alien fragrances. All I could see was the circle of blue sky above, and perhaps a hundred feet below us the pale green mist of which Jim had spoken. It was like a level floor of cloud, impenetrable to the vision. The rock-fall entered it and was lost to sight. I felt no discomfort, but both of us were dripping with sweat. I watched with satisfaction Jim’s deep, unhurried breathing.

“Having any trouble?” I asked at last.

“Not much. Now and then I have to put the pedal down. But I think I’m getting the trick.”

“All right,” I said. “Soon we’ll be moving. I don’t believe it will get any worse as we go down.”

“You talk like an old-timer. What’s your idea of this place anyway, Leif?”

“Simple enough. Although the combination hasn’t a chance in millions to be duplicated. Here is a wide, deep valley entirely hemmed in by precipitous clifis. It is, in effect, a pit. The mountains enclosing it are seamed with glaciers and ice streams and there is a constant flow of cold air into this pit, even in summer. There is probably volcanic activity close beneath the valley’s floor, boiling springs and the like. It may be a miniature of the Valley of Ten Thousand Smokes over to the west All this produces an excess of carbon-dioxide. There is most probably a lush vegetation which adds to the product. What we are going into is likely to be a little left-over fragment of the Carboniferous Age — about ten million years out of its time. The warm, heavy air fills the pit until it reaches the layer of cold air we’ve just come from. The mirage is produced where the two meet, by approximately the same causes which produce every mirage. How long it’s been this way. God alone knows. Parts of Alaska never had a Glacial Age — the ice for some reason or another didn’t cover them. When what is New York was under a thousand feet of ice, the Yukon Flats were an oasis filled with all sorts of animal and plant life. If this valley existed then, we’re due to see some strange survivals. If it’s comparatively recent, we’ll probably run across some equally interesting adaptations. That’s about all, except there must be an outlet of some kind somewhere at about this level, otherwise the warm air would fill the whole valley to the top, as gas does a tank. Let’s be going.”

“I begin to hope we find the guns,” said Jim, thoughtfully.

“As you pointed out, they’d be no good against Khalk’ru — what, who, if and where he is,” I said. “But they’d be handy against his attendant devils. Keep an eye out for them — I mean the guns.”

We started down the rock-fall, toward the floor of green mist. The going was not very difficult. We reached the mist without having seen anything of rifles or packs. The mist looked like a heavy fog. We entered it, and that was precisely what it was. It closed around us, thick and warm. The rocks were reeking wet and slippery, and we had to feel for every foot of the way. Twice I thought our numbers were up. How deep that mist was, I could not tell, perhaps two or three hundred feet — a condensation brought about by the peculiar atmospheric conditions that produced the mirage.

The mist began to lighten. It maintained its curious green tint, but I had the idea that this was due to reflection from below. Suddenly it thinned to nothing. We came out of it upon a breast where the falling rocks had met some obstruction and had piled up into a barrier about thrice my height. We climbed that barrier.

We looked upon the valley beneath the mirage.

It lay a full thousand feet beneath us. It was filled with pale green light like that in a deep forest glade. That light was both lucent and vaporous, lucent where we stood, but hiding the distance with misty curtains of pallid emerald. To the north and on each side as far as I could see, and melting into the vaporous emerald curtains, was a vast carpet of trees. Their breath came pulsing up to me, jungle-strong, laden with the unfamiliar fragrances. At left and right, the black cliffs fell sheer to the forest edge.

“Listen!” Jim caught my arm.

At first only a faint tapping, then louder and louder, we heard from far away the beating of drums, scores of drums, in a strange staccato rhythm — shrill, mocking, jeering! But they were no drums of Khalk’ru! In them was nothing of that dreadful trampling of racing feet upon a hollow world.

They ceased. As though in answer, and from an entirely different direction, there was a fanfarade of trumpets, menacing, warlike. If brazen notes could curse, these did. Again the drums broke forth, still mocking, taunting, defiant.

“Little drums,” Jim was whispering. “Drums of —” He dropped down from the rocks, and I followed. The barrier led to the east, dipping steadily downward. We followed its base. It stood like a great wall between us and the valley, barring our vision. We heard the drums no more. We descended five hundred feet at least before the barrier ended. At its end was another rock slide like that down which the rifles and pack had fallen.

We stood studying it. It descended at an angle of about forty-five degrees, and while not so smooth as the other, it had few enough foot-holds.

The air had steadily grown warmer. I’; was not an uncomfortable heat; there was a queer tingling life about it, an exhalation of the crowding forest or of the valley itself, I thought. It gave me a feeling of rampant, reckless life, a heady exaltation. The pack had grown tiresome. If we were to negotiate the slide, and there seemed nothing else to do, I couldn’t very well carry it. I unslung it.

“Letter of introduction” I said, and sent it slithering down the rock.

“Breathe deep and slow, you poor ass,” said Jim, and laughed.

His eyes were bright; he looked happy, like a man from whom some burden of fear and doubt has fallen. He looked, in fact, as I had felt when I had taken up that challenge of the unknown not so long before. And I wondered.

The slithering pack gave a little leap, and dropped completely out of sight. Evidently the slide did not go all the way to the valley floor, or, if so, it continued at a sharper angle at the point of the pack’s disappearance.

I let myself over cautiously, and began to worm down the slide flat on my belly, Jim following. We had negotiated about three-quarters of it when I heard him shout. Then his falling body struck me. I caught him with one hand, but it broke my own precarious hold. We went rolling down the slide and dropped into space. I felt a jarring shock, and abruptly went completely out.