"I had to drag it out so that I would be sure to be invisible when I had returned here," I explained.

"And now what?" asked Ptor Fak.

I found his head and placed my lips close to one of his ears. "After Rojas comes," I whispered, "we'll cross the roof to the quarters of the slave women and get Llana of Gathol. In the meantime, you climb this tree which overhangs the roof and wait for us up there."

"Whistle when you come up," he said, and left me.

Invisibility I discovered was most disconcerting; I could see no part of my body; I was only a voice without visible substance—a voice standing in an apparently deserted courtyard which might be filled with enemies, as far as I knew. I couldn't even have heard them had there been any there, for the Invaks have taken the precaution of covering all the metal parts of their accouterments so that there is not the usual clank of metal upon metal when they move about.

Knowing as I did that a search for me must have been instituted, I felt positive that there must be Invak warriors in the courtyard, notwithstanding the fact that I neither heard nor saw anyone.

As I waited for Rojas, I took the precaution of not moving about lest I inadvertently bump into someone who might require me to identify myself; but I could not prevent someone from bumping into me, and that is exactly what happened. Hands were laid upon me and a gruff voice demanded, "Who are you?"

Here was a pretty kettle of fish. What was I to do? I doubted that I could pass myself off as an Invak—I knew too little about them to do that successfully; so, I did the next best thing that occurred to me.

"I am the ghost of Motus," I said, in a sepulchral voice. "I am searching for the man who killed me, but he is not here."

The hands relinquished their hold upon me; I could almost feel the fellow shrink away from me, and then another voice said, "Ghost of Motus nothing—I recognize that voice—it is the voice of the slave who killed Motus. Seize him!"

I jumped to one side but I jumped into the arms of another voice, and it seized me. "I have him!" cried the voice. "How did you achieve the secrets of invisibility, slave?"

With my left hand I groped for the hilt of the fellow's sword; and when I found it, I said, "You have made a mistake," and drove his sword through the heart of the voice.

There was a single piercing scream, and I was free. Holding my sword point breast high, I turned and ran for the tree by which Ptor Fak had mounted to the roof. One of my shoulders brushed a body, but I reached the tree in safety.