“I hid in the vault,” continued Marakinoff, “and I saw that which comes from here come out. I waited⁠—long hours. At last, when the moon was low, it returned⁠—ecstatically⁠—with a man, a native, in embrace enfolded. It passed through the door, and soon then the moon became low and the door closed.

“The next night more confidence was mine, yes. And after that which comes had gone, I looked through its open door. I said, ‘It will not return for three hours. While it is away, why shall I not into its home go through the door it has left open?’ So I went⁠—even to here. I looked at the pillars of light and I tested the liquid of the Pool on which they fell. That liquid, Dr. Goodwin, is not water, and it is not any fluid known on Earth.” He handed me a small vial, its neck held in a long thong.

“Take this,” he said, “and see.”