A soft hand caressed my cheek and a voice, tense with nervousness said, "Live! Live for me! I shall return at midnight and you must be here;" then she was gone.

For some reason or other which I cannot explain, her words quieted my nerves.

They gave me confidence that at midnight I should be free. Her presence reminded me that she had dropped something into my pocket pouch and I opened it casually and put my hand into it. My fingers came in contact with a number of spheres, about the size of marbles, and I knew that the secret of invisibility was mine.

I moved close to Ptor Fak; and once again with the remaining bit of wire I picked the lock of his shackle, and then I handed him one of the spheres that Rojas had given me.

I leaned very close to his ear. "Take this," I whispered; "in an hour you will be invisible. Go to the far end of the courtyard and wait. When I return I too shall be invisible and when I whistle thus, answer me." I whistled a few of the opening notes of the national anthem of Helium, a signal that Dejah Thoris and I had often used.

"I understand," said Ptor Fak.

"What do you understand?" demanded a voice.

Doggonit! there was that invisibility nemesis again and now all our plans might be knocked into a cocked hat. How much had the fellow heard? What had he seen? I trembled inwardly, fearing the answer. Then I felt hands at my ankle and saw my shackle fall open.

"Well," repeated the voice peremptorially, "what was it that you understood?"

"I was just telling Ptor Fak," I said, "how I was going to kill Motus, and he said he understood perfectly."

"So you think you are going to kill Motus, do you?" demanded the voice. "Well, you are going to be very much surprised for a few minutes, and after that you will be dead. Come along with me; the duel is about to take place."

I breathed a sigh of relief. The fellow had evidently seen or heard nothing of any importance.

"I'll see you later, Ptor Fak," I said.

"Good-by and good luck," he replied. And then, accompanied by the warrior, I entered a city street on my way to the throne room of Ptantus, jeddak of Invak.

Chapter 9

"So you think you're pretty good with the sword," said the warrior walking at my side and who was now visible to me.

"Yes," I replied.

"Well, you're going to get a lesson in swordsmanship tonight. Of course it won't do you much good because after it is all over you will be dead."

"You are very encouraging," I said, "but if you are fond of Motus, I suggest that you save your encouragement for him. He is going to need it."