No one seemed to be pursuing her, but I closed the door as she had requested and turned toward her for an explanation.

"What is the matter?" I demanded. "From whom were you running?"

"From him." She shuddered. "Oh, he is horrible. Hide me; don't let him get me, please!"

"Whom do you mean? Who is horrible?"

She stood there trembling and wide-eyed, staring past me at the door, like one whom terror had demented.

"Him," she whispered. "Who else could it be?"

"You mean--?"

She came close and started to speak; then she hesitated. "But why should I trust you? You are one of his creatures. You are all alike in this terrible place."

She was standing very close to me now, trembling like a leaf. "I cannot stand it!" she cried. "I will not let him!" And then, so quickly that I could not prevent her, she snatched the dagger from my harness and turned it upon herself.

But there I was too quick for her, seizing her wrist before she could carry out her designs.

She was a delicate-looking creature, but her appearance belied her strength.

However, I had little difficulty in disarming her; and then I backed her toward the bench and forced her down upon it.

"Calm yourself," I said; "you have nothing to fear from me-nothing to fear from anybody while I am with you. Tell me what has happened. Tell me whom you fear."

She sat there staring into my eyes for a long moment, and presently she commenced to regain control of herself. "Yes," she said presently, "perhaps I can trust you. You make me feel that way-your voice, your looks."

I laid my hand upon her shoulder as one might who would quiet a frightened child. "Do not be afraid," I said; "tell me something of yourself. What is your name?"

"Zanda," she replied.

"You live here?"

"I am a slave, a prisoner,"

"What made you scream?" I asked.

"I did not scream," she replied; "that was another. He tried to get me, but I eluded him, and so he took another. My turn will come. He will get me. He gets us all."

"Who? Who will get you?"

She shuddered as she spoke the name. "Fal Sivas," she said, and there was horror in her tone.

I sat down on the bench beside her and laid my hand on hers. "Quiet yourself," I said; "tell me what all this means. I am a stranger here. I just entered the service of Fal Sivas tonight."

"You know nothing, then, about Fal Sivas?" she demanded.

"Only that he is a wealthy inventor and fears for his life."

"Yes, he is rich; and he is an inventor, but not so great an inventor as he is a murderer and a thief. He steals ideas from other inventors and then has them murdered in order to safeguard what he has stolen. Those who learn too much of his inventions die. They never leave this house. He always has an assassin ready to do his bidding; sometimes here, sometimes out in the city; and he is always afraid of his life.

"Rapas the Ulsio is his assassin now; but they are both afraid of Ur Jan, chief of the guild of assassins; for Ur Jan has learned that Rapas is killing for Fal Sivas for a price far lower than that charged by the guild."

"But what are these wonderful inventions that Fal Sivas works upon?" I asked.

"I do not know all of the things that he does, but there is the ship. That would be wonderful, were it not born of blood and treachery."

"What sort of a ship?" I asked.

"A ship that will travel safely through interplanetary space. He says that in a short time we shall be able to travel back and forth between the planets as easily as we travel now from one city to another."

"Interesting," I said, "and not so very horrible, that I can see."

"But he does other things-horrible things. One of them is a mechanical brain."

"A mechanical brain?"

"Yes, but of course I cannot explain it. I have so little learning. I have heard him speak of it often, but I do not understand.

"He says that all life, all matter, are the result of mechanical action, not primarily, chemical action. He holds that all chemical action is mechanical.

"Oh, I am probably not explaining it right. It is all so confusing to me, because I do not understand it; but anyway he is working on a mechanical brain, a brain that will think clearly and logically, absolutely uninfluenced by any of the extraneous media that affect human judgments."

"It seems rather a weird idea," I said, "but I can see nothing so horrible about it."

"It is not the idea that is horrible," she said; "it is the method that he employs to perfect his invention. In his effort to duplicate the human brain, he must examine it. For this reason he needs many slaves. A few he buys, but most of them are kidnaped for him."

She commenced to tremble, and her voice came in little broken gasps. "I do not know; I have not really seen it; but they say that he straps his victims so that they cannot move and then removes the skull until he has exposed the brain; and so, by means of rays that penetrate the tissue, he watches the brain function."

"But his victims cannot suffer long," I said; "they would lose consciousness and die quickly."

She shook her head. "No, he has perfected drugs that he injects into their veins so that they remain alive and are conscious for a long time. For long hours he applies various stimuli and watches the reaction of the brain. Imagine if you can, the suffering of his poor victims.

"Many slaves are brought here, but they do not remain long. There are only two doors leading from the building, and there are no windows in the outer walls.

"The slaves that disappear do not leave through either of the two doorways. I see them today; tomorrow they are gone, gone through the little doorway that leads into the room of horror next to Fal Sivas's sleeping quarters.

"Tonight Fal Sivas sent for two of us, another girl and myself. He purposed using only one of us. He always examines a couple and then selects the one that he thinks is the best specimen, but his selection is not determined wholly by scientific requirements. He always selects the more attractive of the girls that are summoned.

"He examined us, and then finally he selected me. I was terrified. I tried to fight him off. He chased me about the room, and then he slipped and fell; and before he could regain his feet, I opened the door and escaped. Then I heard the other girl scream, and I knew that he had seized her, but I have won only a reprieve. He will get me; there is no escape. Neither you nor I will ever leave this place alive."

"What makes you think that?" I inquired.

"No one ever does."

"How about Rapas?" I asked. "He comes and goes apparently as he wishes."

"Yes, Rapas comes and goes. He is Fal Sivas's assassin. He also aids in the kidnaping of new victims. Under the circumstances he would have to be free to leave the building. Then there are a few others, old and trusted retainers, really partners in crime, whose lives Fal Sivas holds in the palm of his hand; but you may rest assured that none of these know too much about his inventions. The moment that one is taken into Fal Sivas's confidence, his days are numbered.

"The man seems to have a mania for talking about his inventions. He must explain them to someone. I think that is because of his great egotism. He loves to boast. That is the reason he tells us who are doomed so much about his work. You may rest assured that Rapas knows nothing of importance. In fact, I have heard Fal Sivas say that one thing that endeared Rapas to him is the assassin's utter stupidity. Fal Sivas says that if he explained every detail of an invention to him, Rapas wouldn't have brains enough to understand it."

By this time the girl had regained control of herself; and as she ceased speaking, she started toward the doorway. "Thank you so much," she said, "for letting me come in here. I shall probably never see you again, but I should like to know who it is who has befriended me."