So I went on, feeling my way through the thick silent fog. I was able to see only a few inches ahead of me for hours. Then, abruptly the trail grew clearer. Until, at last I was moving in the shadowless, unearthly mist over hard-packed snow, following the clearly marked footprints of a girl's sandals. Then they vanished without warning, those prints, and I stood hesitant, staring around. I could see nothing, but a brighter glow in the misty canopy overhead marked the sun's position. I knelt and brushed away the snow with my hands, hoping to undo the wind's concealing work. But I found no more footprints. Finally I took my bearings as well as I could and ploughed ahead in the general direction the girl had been traveling. My compass told me I was heading due north. The fog was a living, sentient thing now, secretive, shrouding the secret that lay beyond its gray wall. Suddenly I was conscious of a change. An electric tingle coursed through my body. Abruptly the fog-wall brightened. Dimly, as through a translucent pane, I could make out vague images ahead of me. I began to move toward the images--and suddenly the fog was gone! Before me lay a valley. Blue-white moss carpeted it except where reddish boulders broke the blueness. Here and there were trees--at least I assumed they were trees, despite their unfamiliar outline. They were like banyans, having dozens of trunks narrow as bamboo. Blue-leafed, they stood like immense bird-cages on the pallid moss. The fog closed in behind the valley and above it. It was like being in a huge sun-lit cavern. I turned my head, saw a gray wall behind me. Beneath my feet the snow was melting and running in tiny, trickling rivulets among the moss. The air was warm and stimulating as wine. A strange and abrupt change. Impossibly strange! I walked toward one of the trees, stopped at a reddish boulder to examine it. And surprise caught at my throat. It was an artifact--a crumbling ruin, the remnant of an ancient structure whose original appearance I could not fathom. The stone seemed iron-hard. There were traces of inscription on it, but eroded to illegibility. And I never did learn the history of those enigmatic ruins.... They did not originate on Earth. There was no sign of the native girl, and the resilient moss retained no tracks. I stood there, staring around, wondering what to do now. I was tense with excitement. But there was little to see. Just that valley covering perhaps a half-mile before the fog closed in around it. Beyond that--I did not know what lay beyond that.