Caliban

“Self-preservation,” Kresh said, still keeping his eye and his blaster on Ariel. “Fredda Leving was about to discover that Ariel was the free-matrix robot of the two gravitonic brain units in that test Gubber Anshaw ran. You remember, Gubber. A double-blind test. Fredda Leving didn’t tell you, but she gave you one robot with Three Laws and one without. It was a test to see if a free-matrix gravitonic brain could integrate the Three Laws. Well, maybe a free-matrixcan learn Laws-except Ariel managed to invent her own Laws of self-preservation first.”

“But Gubber explained that to me!” Tonya protested. “He said that the test unit would be destroyed, and the control unit placed in service. Ariel was the control unit.”

“Yes, she was,” Alvar Kresh agreed. “ At least she wasafter she managed to switch herself with the real control the night before the test. She had the whole night to find a way to switch the labels between herself and the real control.”

“But surely the real control would have spoken up!” Tonya protested.

“No,” Fredda said, her voice faint and quavering. “The test

pairs in such cases are under very strict ordersnot to reveal which is which, to prevent test bias. The real control must have gone to its destruction knowing the truth but bound not to speak.”

Suddenly Fredda’s eyes widened, and she spoke again, in a stronger voice. “Inventory! I still can’t recall that night itself, but I can remember thinking that I had to go over the brain inventory.”

“Yes!” Gubber said. “I remember. You said there was something wrong with the brain list-”

“And you said it in front of Tonya, Gubber, and Ariel,” Kresh said. “ Ariel realized that you were going to work through the serial numbers on the test and discover that the control unit had been destroyed instead of her. So she waited in Gubber’s lab while you argued with Madame Welton, knowing you would return there once the argument was over.

“Then she did exactly what she had planned to do: cosh you on the head with a nice, precise blow calculated to induce amnesia. That was my other big mistake. I assumed that the attack was attempted murder, even though the attackerhad to know Fredda Leving was still alive after the attack. But if it was attempted murder, then it could not be a Lawless robot, because a robot would not have left the job half-done.”

“Then why do you think I did it?” Ariel asked.

“I ordered you to be quiet,” Kresh said harshly. “You’re not doing too well in your Three Law imitation all of a sudden. You didn’t want her dead. You wanted her to forget all about the inventory. And that you didexactly right. The med-robots say it is highly unlikely that Dr. Leving will ever regain her memory of that evening’s events.”

“But why didn’t she want to kill me?” Fredda asked.

“Because if you died, then the Limbo Project would fold,” Tonya Welton said in a voice that was suddenly flat and cold. “I’m beginning to see the logic of it. Without Fredda Leving to push for the New Law robots, Limbo would fail. That would be inevitable in the political uproar over your murder. Think how bad the situation has been, even though you lived. If you had been killed, it’ d be close to a certainty that all the Settlers would have been thrown off the planet. And I would not have Ariel with me if I was deported.”

Tonya Welton, ashen-faced, moved forward a cautious step or two and took a good long look at Ariel. “What you ‘re telling me, Sheriff, is that I have been spending my days and nights with a potentially homicidal robot that was playacting the part of my helpful companion.” Tonya looked Ariel straight in the eye. “Is that right?” she asked, a strained quaver in her voice.

“Yes, ma’am. I’m afraid that’s about the size of it.”

“And you were there,” Tonya said to Ariel, “day after day, listening to all my secrets, night after night, watching-watching everything! I trusted you!” Tonya looked toward Gubber, who seemed as horrified as she was, then pointed at Ariel and looked back toward the Sheriff. “This, thisthing could have killed me whenever it liked.” Suddenly Tonya laughed, a reedy, panicky bark that had as much horror as humor behind it. “Stars in the sky, but for the first time in my life I know why you people need the Three Laws.”