"A technically advanced race coming up against a more backward one?" hazarded the younger man.
"Could be. Let's go forward some." The incoming tide was washing well up on the reef. Ashe had to don his mask as he plunged head and shoulders under water to make the necessary adjustment.
Once more he pressed the button. And Ross's gasp was echoed by one from the girl. The cliff again, but there was no castle dominating it, only a ruin, hardly more than rubble. Now, above the sites of the saucer depressions great pylons of silvery metal, warmed into fire brilliance by the sunset, raked into the sky like gaunt, skeleton fingers. There were no ships, no signs of any life. Even the vegetation which had showed on shore had vanished. There was an atmosphere of stark abandonment and death which struck the Terrans forcibly.
Those pylons, Ross studied them. Something familiar in their construction teased his memory. That refuel planet where the derelict ship had set down twice, on the voyage out and on their return. That had been a world of metal structures, and he believed he could trace a kinship between his memory of those and these pylons. Surely they had no connection with the earlier castle on the cliff.
Once more Ashe ducked to reset the probe. And in the fast-fading light they watched a third and last picture. But now they might have been looking at the island of the present, save that it bore no vegetation and there was a rawness about it, a sharpness of rock outline now vanished.
Those pylons, were they the key to the change which had come upon this world? What were they? Who had set them there? For the last Ross thought he had an answer. They were certainly the product of the galactic empire. And the castle ... the ships ... natives ... settlers? Two widely different eras, and the mystery still, lay between them. Would they ever be able to bring the key to it out of time?
They swam for the shore where Ui had a fire blazing and their supper prepared.
"How many years lying between those probes?" Ross pulled broiled fish apart with his fingers.
"That first was ten thousand years ago, the second," Ashe paused, "only two hundred years later."
"But"—Ross stared at his superior—"that means——"