There was another possibility I mentioned to my father — perhaps the planet had been in our system all the time, but had been undiscovered, unlikely though that might be, given the thousands of years of study of the skies by men, from the shambling creatures of the Neander Valley to the brilliant intellects of Mount Wilson and Palomar. To my surprise, this absurd hypothesis was welcomed by my father.

"That," he said with animation, "is the Theory of the Sun Shield." He added, "That is why I like to think of the planet as the Counter-Earth, not only because of its resemblance to our native world, but because, as a matter of fact, it is placed as a counterpoise to the Earth. It has the same plane of orbit and maintains its orbit in such a way as always to keep The Central Fire between it and its planetary sister, our Earth, even though this necessitates occasional adjustments in its speed of revolution."

"But surely," I protested, "its existence could be discovered. One can't hide a planet the size of the Earth in our own solar system! It's impossible!"

"You underestimate the Priest-Kings and their science," said my father, smiling. "Any power that is capable of moving a planet — and I believe the Priest-Kings possess this power — is capable of effecting adjustments in the motion of the planet, such adjustments as might allow it to use the sun indefinitely as a concealing shield."

"The orbits of the other planets would be affected," I pointed out.

"Gravitational perturbations," said my father, "can be neutralized." His eyes shone. "It is my belief," he said, "that the Priest-Kings can control the forces of gravity, at least in localized areas, and, indeed, that they do so. In all probability their control over the motion of the planet is somehow connected with this capacity. Consider certain consequences of this power. Physical evidence, such as light or radio waves, which might reveal the presence of the planet, can be prevented from doing so. The Priest-Kings might gravitationally warp the space in their vicinity, causing light or radio waves to be diffused, curved, or deflected in such a way as not to expose their world."

I must have appeared unconvinced.

"Exploratory satellites can be similarly dealt with," added my father. He paused. "Of course, — I only propose hypotheses, for what the Priest-Kings do and how it is done is known only to them."

I drained the last sip of the heady wine in the metal goblet.

"Actually," said my father, "there is evidence of the existence of the Counter-Earth."

I looked at him.

"Certain natural signals in the radio band of the spectrum," said my father.

My astonishment must have been obvious.

"Yes," he said, "but since the hypothesis of another world is regarded as so incredible, this evidence has been interpreted to accord with other theories; sometimes even imperfections in instrumentation have been supposed rather than admit the presence of another world in our solar system."

"But why would this evidence not be understood?" I asked.

"Surely you know," he laughed, "one must distinguish between the data to be interpreted and the interpretation of the data, and one chooses, normally, the interpretation that preserves as much as possible of the old world view, and, in the thinking of the Earth, there is no place for Gor, its true sister planet, the Counter-Earth."

My father had finished speaking. He rose and gripped me by the shoulders, held me for a moment and smiled. Then silently the door in the wall slid aside, and he strode from the room. He had not spoken to me of my role or destiny, whatever it was to be. He did not wish to discuss the reason for which I had been brought to the Counter-Earth, nor did he explain to me the comparatively minor mysteries of the envelope and its strange letter. Most keenly perhaps, I missed that he had not spoken to me of himself, for I wanted to know him, that kindly remote stranger whose bones were in my body, whose blood flowed in mine — my father.

I now inform you that what I write of my own experience I know to be true, and that what I have accepted on authority I believe to be true, but I shall not be offended if you disbelieve, for 1, too, in your place, would refuse to believe. Indeed, on the small evidence I can present in this narrative, you are obliged, in all honesty, to reject my testimony or at the very least to suspend judgment. In fact, there is so little probability that this tale will be believed that the Priest-Kings of Sardar, the Keepers of the Sacred Place, have apparently granted that it may be recorded. I am glad of this, because I must tell this story. I have seen things of which I must speak, even if, as it is said here, only to the Towers.

Why have the Priest-Kings been so lenient in this case — those who control this second earth? I think the answer is simple. Enough humanity remains in them, if they are human, for we have never seen them, to be vain; enough vanity remains in them to wish to inform you of their existence, if only in a way that you will not accept or be able to consider seriously. Perhaps there is humor in the Sacred Place, or irony. After all, suppose you should accept this tale, should learn of the Counter-Earth and of the Voyages of Acquisition, what could' you do? You could do nothing, you with your rudimentary technology of which you are so proud — you could do nothing at least for a thousand years, and by that time, if the Priest-Kings choose, this planet will have found a new sun, and new peoples to populate its verdant surface.