Our ship had settled quietly to the ground beside that of Gar Nal. I caused the door in the port side to be opened and the ladder lowered. Still there was no sign of life either on the other craft or elsewhere about the castle. A deathly silence hung like a heavy mantle over the entire scene.

Just a moment I stood in the doorway looking about; and then I descended to the ground, followed by Jat Or and Zanda.

Before us loomed the castle, a strange weird building of unearthly architecture, a building of many towers of various types, some of them standing alone and some engaged in groups.

Partially verifying Fal Sivas's theory of the tremendous mineral wealth of the satellite, the walls of the structure before us were constructed of blocks of precious stones so arranged that their gorgeous hues blended and harmonized into a mass of color that defied description.

At the moment, however, I gave but cursory attention to the beauties of the pile, turning my attention instead to Gar Nal's ship. A door in its side, similar to that in our ship, was open; and a ladder depended to the ground.

I knew that in ascending that ladder, a man would be at great disadvantage if attacked from above; but there was no alternative. I must discover if there were anyone on board.

I asked Zanda to stand at a little distance, so that she could see into the interior of the ship and warn me if an enemy exhibited himself. Then I mounted quickly.

As the ship was already resting on the ground, I had only to ascend a few rungs of the ladder before my eyes were above the level of the cabin floor. A quick glance showed me that no one was in sight, and a moment later I stood inside the cabin of Gar Nal's ship.

The interior arrangement was slightly different from that of Fal Sivas's, nor was the cabin as richly furnished.

From the cabin, I stepped into the control room. No one was there. Then I searched the after part of the ship. The entire craft was deserted.

Returning to the ground, I reported my findings to Jat Or and Zanda.

"It is strange," remarked Jat Or, "that no one has challenged us or paid any attention to our presence. Can it be possible that the whole castle is deserted?"

"There is something eerie about the place," said Zanda, in low, tense tones.

"Even the silence seems fraught with suppressed sound. I see no one, I hear no one, and yet I feel-I know not what."

"It is mysterious," I agreed. "The deserted appearance of the castle is belied by the well-kept grounds. If there is no one here now, it has not been deserted long."

"I have a feeling that it is not deserted now," said Jat Or. "I seem to feel presences all around us. I could swear that eyes were on us-many eyes, watching our every move."

I was conscious of much the same sensation myself. I looked up at the windows of the castle, fully expecting to see eyes gazing down upon us; but in none of the many windows was there a sign of life. Then I called aloud, voicing the common peace greeting of Barsoom.

"Kaor!" I shouted in tones that could have been heard anywhere upon that side of the castle. "We are travellers from Barsoom. We wish to speak to the lord of the castle."

Silence was my only answer.

"How uncanny!" cried Zanda. "Why don't they answer us? There must be someone here; there is someone here. I know it! I cannot see them, but there are people here. They are all around us."

"I am sure that you are right, Zanda," I said. "There must be someone in that castle, and I am going to have a look inside it. Jat Or, you and Zanda wait here."

"I think we should all go together," said the girl.

"Yes," agreed Jat Or; "we must not separate."

I saw no valid objection to the plan, and so I nodded my acquiescence; then I approached a closed door in the face of the castle wall. Behind me came Jat Or and Zanda.

We had crossed about half the distance from the ship to the door, when at last suddenly, startlingly, the silence was shattered by a voice, terror-ridden, coming from above, apparently from one of the lofty towers overlooking the courtyard.

"Escape, my chieftain!" it cried. "Escape from this horrible place while you may."

I halted, momentarily stunned-it was the voice of Dejah Thoris.

"The princess!" exclaimed Jat Or.

"Yes," I said, "the princess. Come!" Then I started on a run toward the door of the castle; but I had taken scarce a half dozen steps, when just behind me Zanda voiced a piercing scream of terror.

I wheeled instantly to see what danger confronted her.

She was struggling as though in the throes of convulsions. Her face was contorted in horror; her staring eyes and the motions of her arms and legs were such as they might have been had she been battling with a foe, but she was alone. There was no one near her.

Jat Or and I sprang toward her; but she retreated quickly, still struggling.

Darting to our right, and then doubling back, she moved in the direction of the doorway in the castle wall.

She seemed not to move by the power of her own muscles but rather as though she were being dragged away, yet still I saw no one near her.

All that I take so long to tell, occurred in a few brief seconds- before I could cover the short distance to her side.

Jat Or had been closer to her; and he had almost overtaken her when I heard him shout, "Issus! It has me, too."

He went to the ground then as though in a faint, but he was struggling as Zanda struggled-as one who gives battle to an assailant.

As I raced after Zanda my long sword was out, though I saw no enemy whose blood it might drink.

Scarcely ever before in my life have I felt so futile, so impotent. Here was I, the greatest swordsman of two worlds, helpless in defense of my friends because I could not see their foes.

In the grip of what malign power could they be that could seemingly reach out through space from the concealment of some hidden vantage point and hold them down or drag them about as it wished?

How helpless we all were, our helplessness all the more accentuated by the psychological effect of this mysterious and uncanny attack.

My earthly muscles quickly brought me to Zanda's side. As I reached out to seize her and stop her progress toward the castle door, something seized one of my ankles; and I went down. I felt hands upon me-many hands. My sword was torn from my grasp; my other weapons were snatched away.

I fought, perhaps never as I have fought before. I felt the bodies of my antagonists pressing against me. I felt their hands as they touched me and their fists as they struck me; but I saw no one, yet my own blows landed upon solid flesh. That was something. It gave me a little greater sense of equality than before; but I could not understand why, if I felt these creatures, I could not see them.

At least, however, it partially explained the strange actions of Zanda. Her seeming convulsions had been her struggles against these unseen assailants. Now they were carrying her toward the doorway; and as I battled futilely against great odds, I saw her disappear within the castle.

Then the things, whatever they were that assailed me, overpowered me by numbers.

I knew that there were very many of them, because there were so many, many hands upon me.

They bound my wrists behind my back and jerked me roughly to my feet.

I cannot accurately describe my sensations; the unreality of all that had occurred in those few moments left me dazed and uncertain. For at least once in my life, I seemed wholly deprived of the power to reason, possibly because the emergency was so utterly foreign to anything that I had ever before experienced.

Not even the phantom bowmen of Lothar could have presented so unique a situation, for these were visible when they attacked.

As I was jerked to my feet, I glanced about for Jat Or and saw him near me, his hands similarly trussed behind his back.