"What else did you hear?" he demanded.

"Ur Jan ordered that I be killed."

"You must be careful," said Fal Sivas. "Perhaps you had better not go out again at night."

"I can take care of myself," I replied, "and I can be of more service if I can get about at night and talk to people on the outside than I can by remaining cooped up here when I am off duty."

He nodded. "I guess you are right," he said, and then for a moment he sat in deep thought. Finally he raised his head. "I have it!" he exclaimed. "I know who the traitor is."

"Yes?" I asked politely.

"It is Rapas the Ulsio—Ulsio! He is well named."

"You are sure?" I asked.

"It could be no one else," replied Fal Sivas emphatically. "No one else has left the premises but you two since you came. But we will put an end to that as soon as he returns. When he comes back, you will destroy him. Do you understand?"

I nodded.

"It is a command," he said; "see that it is obeyed." For some time he sat in silence, and I could see that he was studying me intently. At last he spoke.

"You have a smattering of the sciences I judge from the fact of your interest in the books in your quarters."

"Only a smattering," I assured him.

"I need such a man as you," he said, "if I could only find someone whom I might trust. But who can one trust?" He seemed to be thinking aloud. "I am seldom wrong," he continued musingly. "I read Rapas like a book. I knew that he was mean and ignorant and at heart a traitor."

He wheeled suddenly upon me. "But you are different. I believe that I can take a chance with you, but if you fail me-" he stood up and faced me, and I never saw such a malevolent expression upon a human face before. "If you fail me, Vandor, you shall die such a death as only the mind of Fal Sivas can conceive."

I could not help but smile. "I can die but once," I said.

"But you can be a long time at the dying, if it is done scientifically." But now he had relaxed, and his tone was a little bantering. I could imagine that Fal Sivas might enjoy seeing an enemy die horribly.

"I am going to take you into my confidence—a little just a little," he said.

"Remember that I have not asked it," I replied, "that I have not sought to learn any of your secrets."

"The risk will be mutual," he said, "your life against my secrets. Come, I have something to show you."

He led me from the room, along the corridor past my quarters, and up the ramp to the forbidden level above. Here we passed through a magnificently appointed suite of living quarters and then through a little door hidden behind hangings, and came at last into an enormous loft that extended upward to the roof of the building, evidently several levels above us.