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——"

"That there was a war or some drastic form of invasion, yes."

"You mean that the star people arrived and just took over this whole planet?" Karara asked. "But why? And those pylons, what were they for? How much later was that last picture?"

"Five hundred years."

"The pylons were gone, too, then," Ross commented. "But why—?" he echoed Karara's question.

Ashe had taken up his notebook, but he did not open it. "I think"—there was a sharp, grim note in his voice—"we had better find out."

"Put up a gate?"

Ashe broke all the previous rules of their service with his answer:

"Yes, a gate."

4

Storm Menace

"We have to know." Ashe leaned back against the crate they had just emptied. "Something was done here—in two hundred years—and then, an empty world."

"Pandora's box." Ross drew a hand across his forehead, smearing sweat and fine sand into a brand.

Ashe nodded. "Maybe we run that risk, loosing all the devils of the aliens. But what if the Reds open the box first on one of their settlement worlds?"

There it was again, the old thorn which prodded them into risks and recklessness. Danger ahead on both paths. Don't risk trying to learn galactic secrets, but don't risk your enemy's learning them either. You held a white-hot iron in both hands in this business. And Ashe was right, they had stumbled on something here which hinted that a whole world had been altered to suit some plan. Suppose the secret of that alteration was discovered by their enemies?

"Were the ship and castle people natives?" Ross wondered aloud.

"Just at a guess they were, or at least settlers who had been established here so long they had developed a local form of civilization which was about on the level of a feudal society."

"You mean because of the castle and the rock bombardment. But what about the ships?"

"Two separate phases of a society at war, perhaps a more progressive against a less technically advanced. American warships paying a visit to the Shogun's Japan, for example."

Ross grinned. "Those warships didn't seem to fancy their welcome. They steered out to sea fast enough when the rocks began to fall."

"Yes, but the ships could exist in the castle pattern; the pylons could not!"

"Which period are you aiming for first—the castle or the pylons?"

"Castle first, I think. Then if we can't pick up any hints, we'll take some jumps forward until we do connect. Only we'll be under severe handicaps. If we could only plant an analyzer somewhere in the castle as a beginning."

Ross did not show his surprise. If Ashe was talking on those terms, then he was intending to do more than just lurk around a little beyond the gate; he was really planning to pick up alien speech patterns, eventually assume an alien agent identity!

"Gordon!" Karara appeared between two of the lace trees. She came so hastily that the contents of the two cups she carried slopped over. "You must hear what Hori has to say—"

The tall Samoan who trailed her spoke quickly. For the first time since Ross had known him he was very serious, a frown line between his eyes. "There is a bad storm coming. Our instruments register it."

"How long away?" Ashe was on his feet.

"A day ... maybe two...."

Ross could see no change in the sky, islands, or sea. They had had idyllic weather for the six weeks since their planeting, no sign of any such trouble in the Hawaikan paradise.

"It's coming," Hori repeated.

"The gate is half up," Ashe thought aloud, "too much of it set to be dismantled again in a hurry."

"If it's completed," Hori wanted to know, "would it ride out a storm?"

"It might, behind that reef where we have it based. To finish it would be a fast job."

Hori flexed his hands. "We're more brawn than brain in these matters, Gordon, but you've all our help, for what it's worth. What about the ship, does it lift on schedule?"

"Check with Rimbault about that. This storm, how will it compare to a Pacific typhoon?"

The Samoan shook his head. "How do we know? We have not yet had to face the local variety."

"The islands are low," Karara commented. "Winds and water could—"

"Yes! We'd better see Rimbault about a shelter if needed."

If the settlement had drowsed, now its inhabitants were busy. It was decided that they could shelter in the spaceship should the storm reach hurricane proportions, but before its coming the gate must be finished. The final fitting was left to Ashe and Ross, and the older agent fastened the last bolt when the waters beyond the reef were already wind ruffled, the sky darkening fast. The dolphins swam back and forth in the lagoon and with them Karara, though Ashe had twice waved her to the shore.

There was no sunlight left, and they worked with torches. Ashe began his inspection of the relatively simple transfer—the two upright bars, the slab of opaque material forming a doorstep between them. This was only a skeleton of the gates Ross had used in the past. But continual experimentation had produced this more easily transported installation.

Piled in a net were several supply containers ready for an exploring run—extra gill-packs, the analyzer, emergency rations, a medical kit, all the basics. Was Ashe going to try now? He had activated the transfer, the rods were glowing faintly, the slab they guarded having an eerie blue glimmer. He probably only wanted to be sure it worked.

What happened at that moment Ross could never find any adequate words to describe, nor was he sure he could remember. The disorientation of the pass-through he had experienced before; this time he was whirled into a vortex of feeling in which his body, his identity, were rift from him and he lost touch with all stability.