"But why do I not see them?" I demanded.

"You don't know how," he replied. "If you knew how, you could see them as plainly as I do."

"I should like very much to see them," I told him. "Can you tell me how I may do so?"

"I can tell you," he said, "but that does not mean that you will be able to see them. Whether you do or not will depend upon your own mental ability. The reason you do not see them is because by the power of their own minds they have willed that you shall not see them. If you can free your mind of this inhibition, you can see them as plainly as you see me."

"But I don't know just how to go about it."

"You must direct your mind upon theirs in an effort to overcome their wish by a wish of your own. They wish that you should not see them. You must wish that you should see them. They were easily successful with you, because, not expecting such a thing, your mind had set up no defense mechanism against it. Now you have the advantage upon your side, because they have willed an unnatural condition, whereas you will have nature's forces behind you, against which, if your mind is sufficiently powerful, they can erect no adequate mental barrier."

Well, it sounded simple enough; but I am no hypnotist, and naturally I had considerable doubt as to my ability along these lines.

When I explained this to Umka, he growled impatiently.

"You can never succeed," he said, "if you harbor such doubts. Put them aside. Believe that you will succeed, and you will have a very much greater chance for success."

"But how can I hope to accomplish anything when I cannot see them?" I asked.

"And even if I could see them, aside from a brief moment that the door is open when food is brought us, I have no opportunity to see them."

"That is not necessary," he replied. "You think of your friends, do you not, although you cannot see them now?"

"Yes, of course, I think of them; but what has that to do with it?"

"It merely shows that your thoughts can travel anywhere. Direct your thoughts, therefore, upon these Tarids. You know that the castle is full of them, because I have told you so. Just direct your mind upon the minds of all the inhabitants of the castle, and your thoughts will reach them all even though they may not be cognizant of it."

"Well, here goes," I said; "wish me luck."

"It may take some time," he explained. "It was a long time after I learned the secret before I could pierce their invisibility."

I set my mind at once upon the task before me, and kept it there when it was not otherwise occupied; but Umka was a loquacious creature; and having long been denied an opportunity for speech, he was now making up for lost time.

He asked me many questions about myself and the land from which I came, and seemed surprised to think that there were living creatures upon the great world that he saw floating in the night sky.

He told me that his people, the Masenas, lived in the forest in houses built high among the trees. They were not a numerous people, and so they sought districts far from the other inhabitants of Thuria.

The Tarids, he said, had once, been a powerful people; but they had been overcome in war by another nation and almost exterminated.

Their enemies still hunted them down, and there would long since have been none of them left had not one of their wisest men developed among them the hypnotic power which made it possible for them to seemingly render themselves invisible to their enemies.

"All that remain of the Tarids," said Umka, "live here in this castle. There are about a thousand of them altogether, men, women, and children.

"Hiding here, in this remote part of the world, in an effort to escape their enemies, they feel that all other creatures are their foes. Whoever comes to the castle of the Tarids is an enemy to be destroyed."

"They will destroy us, you think?" I asked.

"Certainly," he replied.

"But when, and how?" I demanded.

"They are governed by some strange belief," explained Umka; "I do not understand it, but every important act in their lives is regulated by it. They say that they are guided by the sun and the moon and the stars.

"It is all very foolish, but they will not kill us until the sun tells them to, and then they will not kill us for their own pleasure but because they believe that it will make the sun happy."

"You think, then, that my friends, who are also prisoners here, are still alive and safe?"

"I don't know, but I think so," he replied. "The fact that you are alive indicates that they have not sacrificed the others, for I know it is usually their custom to save their captives and destroy them all in a single ceremony."

"Will they destroy you at the same time?"

"I think they will."

"And you are resigned to your fate, or would you escape if you could?"

"I should certainly escape, if I had the chance," he replied; "but I shall not have the chance; neither will you."

"If I could only see these people and talk to them," I said, "I might find the way whereby we could escape. I might even convince them that I and my friends are not their enemies, and persuade them to treat us as friends. But what can I do? I cannot see them; and even if I could see them, I could not hear them. The obstacles seem insuperable."

"If you can succeed in overcoming the suggestion of their invisibility which they have implanted in your mind," said Umka, "you can also overcome the other suggestion which renders them inaudible to you. Have you been making any efforts along these lines?"

"Yes; I am almost constantly endeavoring to throw off the hypnotic spell."

Each day, near noon, our single meal was served to us. It was always the same.

We each received a large jar of water, I a bowl of food, and Umka a cage containing one of the strange bird-like animals which apparently formed his sole diet.

After Umka had explained how I might overcome the hypnotic spell that had been placed upon me and thus be able to see and hear my captors, I had daily placed myself in a position where, when the door was opened to permit our food to be placed within the room, I could see out and discover if the Tarid who brought our food to us was visible to me.

It was always with a disheartening sense of frustration that I saw the receptacles containing the food and water placed upon the floor just inside the door by invisible hands.

Hopeless as my efforts seemed, I still persisted in them, hoping stubbornly against hope.

I was sitting one day thinking of the hopelessness of Dejah Thoris's situation, when I heard the sound of footsteps in the corridor beyond our door and the scraping of metal against metal, such as the metal of a warrior makes when it scrapes against the buckles of his harness and against his other weapons.

These were the first sounds that I had heard, other than those made by Umka and myself-the first signs of life within the great castle of the Tarids since I had been made a captive there. The inferences to be drawn from these sounds were so momentous that I scarcely breathed as I waited for the door to open.

I was standing where I could look directly out into the corridor when the door was opened.

I heard the lock click. Slowly the door swung in upon its hinges; and there, distinctly visible, were two men of flesh and blood. In conformation they were quite human. Their skins were very fair and white, and in strange contrast were their blue hair and blue eyebrows. They wore short close-fitting skirts of heavy gold mesh and breastplates similarly fabricated of gold. For weapons, each wore a long sword and a dagger. Their features were strong, their expressions stern and somewhat forbidding.

I noted all these things in the few moments that the door remained open. I saw both men glance at me and at Umka, and I was quite sure that neither of them was aware of the fact that they were quite visible to me. Had they known it, I am sure that their facial expressions would have betrayed the fact.