Da Costa, who had come aboard unnoticed by either of us, now tapped me on the arm.

“Doctair Goodwin,” he said, “can I see you in my cabin, sair?”

At last, then, he was going to speak. I followed him.

“Doctair,” he said, when we had entered, “this is a veree strange thing that has happened to Olaf. Veree strange. An’ the natives of Ponape, they have been very much excite’ lately.

“Of what they fear I know nothing, nothing!” Again that quick, furtive crossing of himself. “But this I have to tell you. There came to me from Ranaloa last month a man, a Russian, a doctair, like you. His name it was Marakinoff. I take him to Ponape an’ the natives there they will not take him to the Nan–Matal where he wish to go — no! So I take him. We leave in a boat, wit’ much instrument carefully tied up. I leave him there wit’ the boat an’ the food. He tell me to tell no one an’ pay me not to. But you are a friend an’ Olaf he depend much upon you an’ so I tell you, sair.”

“You know nothing more than this, Da Costa?” I asked. “Nothing of another expedition?”

“No,” he shook his head vehemently. “Nothing more.”

“Hear the name Throckmartin while you were there?” I persisted.

“No,” his eyes were steady as he answered but the pallor had crept again into his face.

I was not so sure. But if he knew more than he had told me why was he afraid to speak? My anxiety deepened and later I sought relief from it by repeating the conversation to O’Keefe.

“A Russian, eh,” he said. “Well, they can be damned nice, or damned — otherwise. Considering what you did for me, I hope I can look him over before the Dolphin shows up.”

Next morning we raised Ponape, without further incident, and before noon the Suwarna and the Brunhilda had dropped anchor in the harbour. Upon the excitement and manifest dread of the natives, when we sought among them for carriers and workmen to accompany us, I will not dwell. It is enough to say that no payment we offered could induce a single one of them to go to the Nan–Matal. Nor would they say why.

Finally it was agreed that the Brunhilda should be left in charge of a half-breed Chinaman, whom both Da Costa and Huldricksson knew and trusted. We piled her long-boat up with my instruments and food and camping equipment. The Suwarna took us around to Metalanim Harbour, and there, with the tops of ancient sea walls deep in the blue water beneath us, and the ruins looming up out of the mangroves, a scant mile from us, left us.

Then with Huldricksson manipulating our small sail, and Larry at the rudder, we rounded the titanic wall that swept down into the depths, and turned at last into the canal that Throckmartin, on his map, had marked as that which, running between frowning Nan–Tauach and its satellite islet, Tau, led straight to the gate of the place of ancient mysteries.

And as we entered that channel we were enveloped by a silence; a silence so intense, so — weighted that it seemed to have substance; an alien silence that clung and stifled and still stood aloof from us — the living. It was a stillness, such as might follow the long tramping of millions into the grave; it was — paradoxical as it may be — filled with the withdrawal of life.

Standing down in the chambered depths of the Great Pyramid I had known something of such silence — but never such intensity as this. Larry felt it and I saw him look at me askance. If Olaf, sitting in the bow, felt it, too, he gave no sign; his blue eyes, with again the glint of ice within them, watched the channel before us.

As we passed, there arose upon our left sheer walls of black basalt blocks, cyclopean, towering fifty feet or more, broken here and there by the sinking of their deep foundations.

In front of us the mangroves widened out and filled the canal. On our right the lesser walls of Tau, sombre blocks smoothed and squared and set with a cold, mathematical nicety that filled me with vague awe, slipped by. Through breaks I caught glimpses of dark ruins and of great fallen stones that seemed to crouch and menace us, as we passed. Somewhere there, hidden, were the seven globes that poured the moon fire down upon the Moon Pool.

Now we were among the mangroves and, sail down, the three of us pushed and pulled the boat through their tangled roots and branches. The noise of our passing split the silence like a profanation, and from the ancient bastions came murmurs — forbidding, strangely sinister. And now we were through, floating on a little open space of shadow-filled water. Before us lifted the gateway of Nan–Tauach, gigantic, broken, incredibly old; shattered portals through which had passed men and women of earth’s dawn; old with a weight of years that pressed leadenly upon the eyes that looked upon it, and yet was in some curious indefinable way — menacingly defiant.

Beyond the gate, back from the portals, stretched a flight of enormous basalt slabs, a giant’s stairway indeed; and from each side of it marched the high walls that were the Dweller’s pathway. None of us spoke as we grounded the boat and dragged it upon a half-submerged pier. And when we did speak it was in whispers.

“What next?” asked Larry.

“I think we ought to take a look around,” I replied in the same low tones. “We’ll climb the wall here and take a flash about. The whole place ought to be plain as day from that height.”

Huldricksson, his blue eyes alert, nodded. With the greatest difficulty we clambered up the broken blocks.

To the east and south of us, set like children’s blocks in the midst of the sapphire sea, lay dozens of islets, none of them covering more than two square miles of surface; each of them a perfect square or oblong within its protecting walls.

On none was there sign of life, save for a few great birds that hovered here and there, and gulls dipping in the blue waves beyond.

We turned our gaze down upon the island on which we stood. It was, I estimated, about three-quarters of a mile square. The sea wall enclosed it. It was really an enormous basalt-sided open cube, and within it two other open cubes. The enclosure between the first and second wall was stone paved, with here and there a broken pillar and long stone benches. The hibiscus, the aloe tree, and a number of small shrubs had found place, but seemed only to intensify its stark loneliness.

“Wonder where the Russian can be?” asked Larry.

I shook my head. There was no sign of life here. Had Marakinoff gone — or had the Dweller taken him, too? Whatever had happened, there was no trace of him below us or on any of the islets within our range of vision. We scrambled down the side of the gateway. Olaf looked at me wistfully.

“We start the search now, Olaf,” I said. “And first, O’Keefe, let us see whether the grey stone is really here. After that we will set up camp, and while I unpack, you and Olaf search the island. It won’t take long.”

Larry gave a look at his service automatic and grinned. “Lead on, Macduff,” he said. We made our way up the steps, through the outer enclosures and into the central square, I confess to a fire of scientific curiosity and eagerness tinged with a dread that O’Keefe’s analysis might be true. Would we find the moving slab and, if so, would it be as Throckmartin had described? If so, then even Larry would have to admit that here was something that theories of gases and luminous emanations would not explain; and the first test of the whole amazing story would be passed. But if not — And there before us, the faintest tinge of grey setting it apart from its neighbouring blocks of basalt, was the moon door!

There was no mistaking it. This was, in very deed, the portal through which Throckmartin had seen pass that gloriously dreadful apparition he called the Dweller. At its base was the curious, seemingly polished cup-like depression within which, my lost friend had told me, the opening door swung.

What was that portal — more enigmatic than was ever sphinx? And what lay beyond it? What did that smooth stone, whose wan deadness whispered of ages-old corridors of time opening out into alien, unimaginable vistas, hide? It had cost the world of science Throckmartin’s great brain — as it had cost Throckmartin those he loved. It had drawn me to it in search of Throckmartin — and its shadow had fallen upon the soul of Olaf the Norseman; and upon what thousands upon thousands more I wondered, since the brains that had conceived it had vanished with their secret knowledge?

What lay beyond it?

I stretched out a shaking hand and touched the surface of the slab. A faint thrill passed through my hand and arm, oddly unfamiliar and as oddly unpleasant; as of electric contact holding the very essence of cold. O’Keefe, watching, imitated my action. As his fingers rested on the stone his face filled with astonishment.

“It’s the door?” he asked. I nodded. There was a low whistle from him and he pointed up toward the top of the grey stone. I followed the gesture and saw, above the moon door and on each side of it, two gently curving bosses of rock, perhaps a foot in diameter.

“The moon door’s keys,” I said.

“It begins to look so,” answered Larry. “If we can find them,” he added.

“There’s nothing we can do till moonrise,” I replied. “And we’ve none too much time to prepare as it is. Come!”

A little later we were beside our boat. We lightered it, set up the tent, and as it was now but a short hour to sundown I bade them leave me and make their search. They went off together, and I busied myself with opening some of the paraphernalia I had brought with me.

First of all I took out the two Becquerel ray-condensers that I had bought in Sydney. Their lenses would collect and intensify to the fullest extent any light directed upon them. I had found them most useful in making spectroscopic analysis of luminous vapours, and I knew that at Yerkes Observatory splendid results had been obtained from them in collecting the diffused radiance of the nebulae for the same purpose.

If my theory of the grey slab’s mechanism were correct, it was practically certain that with the satellite only a few nights past the full we could concentrate enough light on the bosses to open the rock. And as the ray streams through the seven globes described by Throckmartin would be too weak to energize the Pool, we could enter the chamber free from any fear of encountering its tenant, make our preliminary observations and go forth before the moon had dropped so far that the concentration in the condensers would fall below that necessary to keep the portal from closing.

I took out also a small spectroscope, and a few other instruments for the analysis of certain light manifestations and the testing of metal and liquid. Finally, I put aside my emergency medical kit.

I had hardly finished examining and adjusting these before O’Keefe and Huldricksson returned. They reported signs of a camp at least ten days old beside the northern wall of the outer court, but beyond that no evidence of others beyond ourselves on Nan–Tauach.

We prepared supper, ate and talked a little, but for the most part were silent. Even Larry’s high spirits were not in evidence; half a dozen times I saw him take out his automatic and look it over. He was more thoughtful than I had ever seen him. Once he went into the tent, rummaged about a bit and brought out another revolver which, he said, he had got from Da Costa, and a half-dozen clips of cartridges. He passed the gun over to Olaf.

At last a glow in the southeast heralded the rising moon. I picked up my instruments and the medical kit; Larry and Olaf shouldered each a short ladder that was part of my equipment, and, with our electric flashes pointing the way, walked up the great stairs, through the enclosures, and straight to the grey stone.

By this time the moon had risen and its clipped light shone full upon the slab. I saw faint gleams pass over it as of fleeting phosphorescence — but so faint were they that I could not be sure of the truth of my observation.

We set the ladders in place. Olaf I assigned to stand before the door and watch for the first signs of its opening — if open it should. The Becquerels were set within three-inch tripods, whose feet I had equipped with vacuum rings to enable them to hold fast to the rock.

I scaled one ladder and fastened a condenser over the boss; descended; sent Larry up to watch it, and, ascending the second ladder, rapidly fixed the other in its place. Then, with O’Keefe watchful on his perch, I on mine, and Olaf’s eyes fixed upon the moon door, we began our vigil. Suddenly there was an exclamation from Larry.

“Seven little lights a............