I sat in silence for a while, thinking of the strange race whose relics we were examining. Only once—never again!—had I gone up the great vent our engineers had opened into the Shadow World. It had been a frightening and unforgettable experience. The multiple layers of my pressure suit had made movement very difficult, and despite their insulation I could sense the unbelievable cold that was all around me.

“What a pity it was,” I mused, “that our emergence destroyed them so completely. They were a clever race, and we might have learned a lot from them.”

“I don’t think we can be blamed,” said Karn. “We never really believed that anything could exist under those awful conditions of near-vacuum, and almost absolute zero. It couldn’t be helped.”

I did not agree. “I think it proves that they were the more intelligent race. After all, they discovered us first. Everyone laughed at my grandfather when he said that the radiation he’d detected from the Shadow World must be artificial.”

Karn ran one of his tentacles over the manuscript.

“We’ve certainly discovered the cause of that radiation,” he said. “Notice the date—it’s just a year before your grandfather’s discovery. The Professor must have got his grant all right!” He laughed unpleasantly. “It must have given him a shock when he saw us coming up to the surface, right underneath him.”

I scarcely heard his words, for a most uncomfortable feeling had suddenly come over me. I thought of the thousands of miles of rock lying below the great city of Callastheon, growing hotter and denser all the way to the Earth’s unknown core. And so I turned to Karn.

“That isn’t very funny,” I said quietly. It may be our turn next.”