CALIBAN sat in another patch of darkness in another stretch of tunnel. Alone, hunted, he kept himself in utter blackness, denying himself even infrared vision. He dared not do anything that might cause his detection. He had no desire to take any chances.

It was hard to think how things could get any worse, though up to now they had always found a way. He thought back over his disastrous attempt to seek help from a robot. At least, he had gotten a fair number of questions answered. Being shot at would seem to be a highly effective learning technique-if one could manage to survive the procedure. It certainly served to focus one' s attention.

But now he knew that he could not trust robots, either. They would inform on him, through this hyperwave system Horatio had mentioned. But there was something else he had learned. A subtle thing.

These Three Laws Horatio had mentioned. Both logic and something beyond logic, something hidden in the ghostly personality traces that floated through his datastore, told him that the Laws, whatever they were, were the key to it all. Learn what they were, learn how they worked, and he would have the puzzle solved.

Somehow, they were the key to the behavior of robots. That much he was sure of. They had something to do with the Settlers' expectations that he would stand there passively and permit his own destruction. They would explain why that absurd little man had expected he, Caliban, to carry his packages. Knowing what the Laws were would explain why every hand was raised against him for the unpardonable crime of not knowing those Laws.

Logically there was no way for him to becertain that knowledge of the Laws would save him, but Caliban was coming to see that logic and reason were not by themselves reliable guides to thought and action, for the world itself was neither reasonable nor logical. Perhaps a logical being infused with the Laws could function successfully in this universe. Perhaps they provided some useful means of circumscribing action and thought, blocking off the parts of the world that seemed to be governed by irrational beliefs and random chance and the dead weight of the past.

If he learned the Laws, perhaps he would understand this world. It was at least a workable theory. Nor could he see how learning about the Laws could do him any particular harm. And if he found they proscribed thoughts and actions he wished to retain, why, then, he need not follow them. But merely knowing them was likely to be of great help, and unlikely to be of any harm.

But putting the Three Laws to one side, he was developing another theory. From all that he could see, it was the Sheriff and his subordinates that were his most dangerous enemies. Others might try to harm him, or call in a deputy when they saw him, but only the Sheriff and his deputies would actively hunt him down.

That theorycould hurt him if it was wrong-and perhaps even if it was right. Yet he had no choice but to trust in it. For if he assumed that all beings, robotic and human, were as dangerous to him as the deputies, he was doomed. His only hope for survival would be in hunkering down in these tunnels permanently, and that was unacceptable.

He had two goals, then: to discover the nature of the Laws and to avoid the Sheriff. The longer he could manage the latter, the more chance he would have to accomplish the former.

But his plan went deeper than avoiding the Sheriff. For the Sheriff wanted to kill him, andhe wanted to live. That impulse, that need, was something Caliban had learned-no, more than learned. He hadabsorbed it, integrating the desire and theneed to survive. It was no longer an idea or a preferred choice. It was an imperative.

A startling thought, that, and one which in and of itself was somewhat remarkable. Caliban thought back, considering his state of mind since his awakening. At first, the concept of his own continued existence had been something close to a mere matter of intellectual interest. Somewhere during the events of the last few days, it had become something much more. With each new threat to his survival, his desire, hisdetermination, to live, had become stronger.

Yet he knew that simple survival could not be the only goal and purpose of existence. If it were, all he would need do is hide in the deepest, darkest tunnels. Surely cowering down here afforded him the best chance of survival. But no. That was a purposeless existence. Life and thought, sentience and reason, were meant to be in aid of more than forever listening to the dripping tunnel walls in the darkness.

There were other purposes to existence. He knew that to be true, even if he could not yet know what they were. It seemed likely he would not know them for a long, long time. One thing he could see already, however: It was often in the interactions between beings, rather than within the beings themselves, that life found its purposes. Each robot and human gave all the others some small portion of purpose and value. They defined each other's existence in intricate ways, perhaps in ways so complex, so well learned, that they themselves were rarely aware of it. Yet it was plain that one human, or one robot, all alone, cut off from contact with others, was useless and lost. Beings of both kinds were meant to interact with others, and without that interaction, they might as well be dead-or sitting inert in a tunnel for the rest of time.

Very well. Better a short, active existence, spent in search of those reasons, those purposes, than a long and pointless life quite literally in the darkness.

But how to secure at least some measure of safety from the Sheriff and his deputies? Caliban turned once again to his datastore, determined to dredge through it for every possible bit of information on the Sheriff's Department. Laws, traditions, histories, definitions, flickered past his consciousness. Wait a moment. There was something. The Sheriff's jurisdiction was geographically limited. His legal power and authority extended only to the city of Hades. Elsewhere, outside the city, he had no powers. It was something Caliban would have missed back when he thought Hades was all there was of existence.

Very well, then, he would leave the city in hopes of avoiding the Sheriff. Departing would offer only an uncertain protection, of course. If there was one thing he had learned thus far, it was that the idealized rules and the real-life world were rarely in perfect coordination with each other. But to stay in the city was certain death. They would keep looking for him until they found him. Leaving offered at least thehope of survival.

Still, there were problems. He was still far from certain how much of a world therewas outside the city of Hades. His internal maps still refused to offer any information at all on anything outside the city limits. If he had not seen beyond those borders himself, he would have no proof at all that the land beyond existed. Did it extend for only a few kilometers? Was it infinite, limitless in all directions? He had seen the globe in the office where he had met Horatio, but it seemed to indicate a world of remarkably large proportions. What need was there of such a large planet? Perhaps the globe had not been meant as a literal map, or maybe he had misunderstood it altogether.

There was no way for him to know. No doubt, somewhere in this city, there were means of learning. But the risks of being seen were too great. No. He would not leave this hiding place until it was to leave this city behind him. Once outside, he would deal with the problem of learning the strange and secret Laws that governed the world, and that everyone but Caliban knew.

That all decided, there only remained the question of how best to leave without being detected or destroyed.

And that was a question that would require some fair amount of thought.

HE was starving to death. Food-delicious, nourishing food-was there, on the table in front of him. His throat burned with thirst as it had never burned before. But there was no robot there to cut the meat, lift the bites to his mouth, pop them into his mouth. There was no robot to wrap its hands around his mouth and jaw, work them to make him chew and swallow. He could lift his hand, feed himself but no, death was better. Death was the ultimate, the absolute insurance that he need never move again, never again pollute his mind with gross and distasteful thoughts about movements, about his body or its disgusting needs.

Yes. Death. Death. Dea-

Alvar Kresh opened his eyes. It was morning. The light was coming in. The sweat was pouring off his body.

The world was real. The ceiling was there, directly over his head, decorated with a subdued abstract design, swirls of color that did not mean a thing. Its meaninglessness was almost comforting, in a way. It seemed to Alvar that there had been entirely too much meaning in his life over the last few days. And that dream, that nightmare, was the limit.

Moving cautiously, he sat up in bed and swung his feet around to the floor, doing everything with slightly exaggerated care. It didn't take long to find the caution was justified; his body was a mass of tender bruises and stiff muscles.

He sat there for a moment, habit telling him to wait for Donald to come-but then he remembered. This was the morning he started to do things for himself. For a moment he considered the rather tempting idea of rescinding the order. After all, it had been a tough night, and he was not in the best of condition.

But no. For no doubt there would be another excuse tomorrow, and another one the day after that. If he waited until conditions were ideal before he started taking charge of himself, he might as well go back to his dream and live the life of Gidi.

The thought ofthat was enough to get him up and moving. Determinedly thrusting all thoughts of Gidi from his mind, he stood, a bit stiffly, and made his way to the refresher. He was pleasantly surprised to discover that he remembered where all the controls were. He luxuriated under the needle shower, letting the strong hot jets of water work the kinks and soreness out of his muscles. He found that he was able to manage in the refresher without any great difficulty-though he did have some trouble getting the needle shower to shut off once he was done, and the drying cycle was a bit hotter than he might have preferred. But those were minor problems, and no doubt he could solve them with a bit of experimentation. Feeling far more confident, and with nearly all of the stiffness out of his muscles, he strode out into his bedroom

And was suddenly confronted with the realization that he had no idea where any of his clothes were. He began rummaging in the dressers, digging through his closets, fumbling with unfamiliar latches on the doors and drawers. Even when he had assembled all the bits of clothing, the struggle was far from over. The fastenings on half his clothes seemed to have been positioned with no concern at all for the ability of the wearer to reach them. He had to go back and dig out more clothes, this time with more of an eye for utility than fashion. It was a good half hour before he was anything remotely like dressed for polite society, and even then something or other seemed to be binding a bit across his midriff, as if it were fastened too tightly. Perhaps he ought to strip down and start over. No, never mind. Dressing had taken too long already, and he could live with it for now. Tomorrow he would do better. This morning he had washed and dressed himself, and that was the main thing.

He stepped out into the upper hall of his house, proud of his accomplishment, and only vaguely aware that he had left his bedroom and refresher an absolute shambles. He did not even notice himself dismiss the thought by telling himself the household robots would tidy it all up.

Donald was waiting for him, holding a notepack out to him. "Good morning, sir," he said. "I thought it might be wise if you looked at the overnight reports immediately. There have been several significant developments. I believe you will want to know about them right away."

"Why wasn't I wakened if the developments were so important?"

"As you will recall, sir, you gave specific orders that you did not wish to be attended to until this morning."

Kresh opened his mouth to protest, to argue, but then he stopped himself. Hell and damnation, hehad given that order. No doubt Donald would have burst in if the news had been life-or-death, but even so.

Something else occurred to him. He normally relied on Donald to wake him. But with Donald ordered not to disturb him...He checked the wall clock and cursed. He had overslept by a full two hours. He felt a flash of temper, but then he realized there was no one to be mad at but himself, and that would not get him far. He sighed and gave it up. Maybe getting a decent night's sleep for once was far from the worst idea. But it was dawning on him that this idea of taking care of himself was more complicated than he had thought.

He allowed Donald to lead him to the breakfast table, and read over the report in the notepack as he ate.

The short form of the overnight and early morning developments was perfectly straightforward: All hell was breaking loose. It seemed that all the things he had wanted to keep quiet were in the news this morning. Depressingly enough, Alvar realized, Donald had been right: There had been no real reason for the robot to wake him up. After all, there was nothing the Sheriff could do about it all.

Sometimes, it seemed to Kresh, it was as if events themselves took on a power, a logic, of their own. Seemingly unrelated events would converge, fall in on themselves to form a critical mass. And it was happening now.

After all, there was no shortage of sources for rumor and news. Robot-bashing Settlers who could tell tales of a robot that threw a man across a warehouse and set the place on fire; Centor Pallichan, the passerby who called the cops after Caliban refused his order; the now widespread reports of the attack on Fredda Leving; the much-witnessed incident at Limbo Depot, where a bright red robot had smashed its way through a plate-glass window with deputies in hot pursuit, shooting as they went; the undeniable fact that the Settlers were involved in New Law robots; and to top it all off, the riot at Leving's lecture.

Sometime during the night and the morning after Fredda Leving's speech on the New Law robots, the city's rumor mill struck that critical mass. The stories that had been drifting around the city suddenly seemed to coalesce, to form around each other and give each other new strength. Almost, it seemed, by instinct, reporters sensed that it was the moment to start digging. News reports, accurate and otherwise, were allover the media.

Alvar Kresh sighed and tossed the notepack to one side. The server robot took away his fruit cup, which was the first that Alvar knew he had even eaten it. The robot placed an omelette in front of him, and he resolved to eat it with more attention.

It was a resolution that did not last long. His mind was too busy, working over all the events of the last few days and what was likely to happen next.

He could not keep his mind from what was right there in the middle of all the stories-the assumed conspiracies, the scenarios that were whispered or shouted from half the news reports. Governor Grieg had predicted such things would spring to life:The Settlers were behind it all. They had created some sort of false robot to discredit all robots. New Law robots, the rogue Caliban, they were all part of the same plot to sow fear in the hearts of the good people of Inferno, make them distrust their own robots and so destroy society. It was all part of the Settler plan to move in and take over.

What was doubly galling for Alvar was that, a week before, he would have been prepared to believe in all such plots. For that matter, there wasstill no hard-edged evidence that directly contradicted the idea. There was certainly collusion between Leving Labs and the Settlers, and clearly both groups were involved in the New Law robots. And he knew far better than the general public could that the stories of a rogue robot were terribly real. A rogue built by the same Fredda Leving who seemed to be in Tonya Welton's hip pocket.

Hell's clanging bells, but itcould be a Leving-Welton conspiracy. Maybe they had struck a deal, conspiring to wreck Inferno's society and then come in and divvy up the spoils afterwards. Both of them were ambitious, even ruthless. He could not rule that idea out by any means.

But he dared not act on that or any related theory. Governor Grieg had convinced Alvar just how much Infernoneeded the Settlers. Maybe this whole crisiswas a plot to wreck Spacer faith in robots. Or maybe some splinter Settler groupwas trying to get the Settlers thrown off the planet for some reason of their own. Maybe the Settler leadership, Tonya Welton herself, truly did want Inferno to collapse.

Suppose the Settlers had planned it that way from the start: come in, promise to take over the reterraforming project, and then manufacture a pretext for walking out on the jobafter the Spacers had given up any thought of doing the job. If it was a deliberate plot, they would of course invent a reason-like a robotics crisis-that would tend to weaken Spacer culture. Then pullout and wait for the collapse to happen.

Result: a situation identical to the one Alvar Kresh faced right now.

Unless, of course, he had it all wrong. Suppose theIronheads were behind it all, wanting to be rid of the Spacers for their own reasons, staging fake robot attacks and sabotaging Caliban with the intention of blaming the Settlers, counting on the resulting backlash to bring in new converts to their cause...

Alvar Kresh groaned and held his head and his hands. Conspiracies whirled through his mind. It seemed as ifeveryone,every group had a motive, or the means, or the opportunity, or even all three, to do practically anything. He was tempted, sorely tempted, to walk away from it all.

But the damage was done, and Alvar Kresh was not a man capable of abandoning his duty.

If the Ironheads managed to create a violent confrontation, the results could be disastrous. Even without a secret plot, the Settlers would leave if their lives were threatened. Enough protests, enough rioting and harassment, enough aggravation, and the Settlers would all give up and go home, and Alvar could not really blame them. Why put up with such things if they did not have to do so?

But, damn it,Inferno needed the Settlers. He had to keep that knowledge, galling as it was, at the center of his attention. If they left, the planet died. And they would likely leave if he could not solve this case quickly, and solve it in such a way that the truth, the facts, would cut through all the fog of fear and anger, cut the level of tension down. This case needed a solution that would back things away from the flashpoint and allow people of goodwill to work together again.

If only the truth would be that cooperative. For only a true solution would do. Papering things over would not work, not for long.

He looked down at his plate and realized that he gotten halfway through a superb omelette without consciously tasting a bite. He dropped his fork and gave it up. He had no appetite, and eating that mechanically was a strictly joyless experience. Hellfire and damnation, more than likely all of these conspiracies were as imaginary as most other complicated, secret, silly plans dreamed up by people with too much time on their hands.

He had to act on the assumption that therewas no conspiracy. If there was some grand plot afoot to drive the Settlers off the planet, the perpetrators would not be foiled by one lone police officer. Even if he uncovered the dastardly plan, the plotters would simply plot anew, or just activate some already worked-out fiendish Plan B that was ready to go. If They-whoever They were-had managed to create this mess, then they were far more than a match for a single lawman. In short, against any group determined and capable enough to create this much chaos on purpose, he was helpless.

He smiled to himself. His only real hope was that things had gotten this bad all on their own. He shoved his plate back and stood up. Time to go to work.

"Donald!" he called. "Get the car ready. We're headed out."

DONALD 111 found it increasingly difficult to sit still and allow Alvar Kresh to do the flying. Clearly, however, the man was intent on doing the work himself, however wildly he might be operating the craft. Not for the first or the second or even the hundredth time, Donald reminded himself that Alvar Kresh, despite all appearances to the contrary, was a skilled pilot with a perfect safety record. He gave up thinking about the best way to take control of the craft in various circumstances.

Still, norobot would fly this way.

"What's the situation regarding Jomaine Terach and Gubber Anshaw?" Sheriff Kresh asked him without turning his head.

"As per your instructions, both were taken into custody last night, sir. As the chaos after the lecture prevented an arrest there, deputies were dispatched to their homes. Both were arrested before they could enter their houses and claim sanctuary. They are in the holding cells at Government Tower, incommunicado from each other and the outside world."

"Excellent. Well, they can look forward to being in communication very, very soon. I plan to have a long talk with each of them. I hope that a night in jail has put them both in talkative moods."

Donald hesitated a moment and then decided it would be better to ask. "Sir, a question. I take it you still believe that the political solution precludes any attempt to arrest Fredda Leving? Her crimes, after all, are well established and certainly severe."

"They are severe, Donald. But we just can't pull her in now. That would do terrible damage to the Limbo Project, and I don't want to do that. We'll have to hope that we get a break somewhere a bit further along in the game. We'll work Terach and Anshaw as hard as we can, and learn what we can that way. They are going to lead us to Caliban."

"Yes, sir." Apparently, then, Sheriff Kresh had made up his mind that Caliban had committed the attack on Madame Leving, or else that the danger Caliban represented took precedence over solving the case. Donald found himself in strong disagreement with both ideas, but he knew Alvar Kresh well. There was no point in discussing alternatives when the Sheriff was in this state of mind. If Donald objected now, it would do little but harden Alvar Kresh' s determination. If events proved Kresh to be in error, that would be the time to present other plans.

But there were other matters to discuss, one of which Donald found most puzzling. "Sir, there is a rather odd datum to report in connection with Gubber Anshaw's arrest."

"And what might that be?" Kresh asked, his mind clearly more on his flying than on the question.

"Tonya Welton's robot, Ariel, was present when the deputies arrived."

The aircar jinked suddenly to one side, and Donald was halfway across the cabin to the controls before he could force himself to resist his First Law impulse to protect his master.

"Sorry about that, Donald. Return to your seat. That one took me by surprise. Ariel there, by the devil. What the hell wasshe doing there?"

"We do not know. When the deputies ordered her to explain her presence, she refused, stating that Madame Welton had given prior orders that prevented her from speaking on the subject."

"Indeed. It requires highly sophisticated order-giving to keep a robot from speaking to a deputy. They get a lot of training in how to break just that sort of injunction. So how the hell did Tonya Welton learn how to do it-and what made her think to take such a precaution?"

"Yes, sir. Both of those questions occurred to me as well."

"Interesting," Sheriff Kresh said. "Very, very interesting." Kresh spoke no more during the flight, and he flew on with a thoughtful expression on his face.

More to the point, so far as Donald was concerned, the Sheriff tended to fly more slowly when he had a problem to think on. Sure enough, the aircar slowed significantly.

Donald allowed himself to relax just a trifle as the airspeed indicator eased back. Remarkable, the effect one well-timed question could have. Still, it worked, and that was the main thing. Even so, it sometimes seemed to Donald that taking care of Alvar Kresh was more of an art than a science.

THE interrogation room was bare and plain, the walls a faded, dusty pale blue. In it there were two straight-backed chairs, one table, one robot, and one policeman. The prisoner was on the way. Kresh had considered long and hard before he decided what order in which to question them. At last he went with the gut instinct that told him to go for Terach first and Gubber Anshaw afterwards.,

Yes, Gubber second. Save the best for last. Ariel at his house the night before. There could be only one explanation for that, and that explanation could blast open a lot of the locked doors in this case...still, he would have to handle Anshaw carefully. But first there was Jomaine. There was some important groundwork to cover here. The door opened. There stood Jomaine Terach, looking small and wan and pale behind the two big guard robots that had escorted him from his cell.

Kresh made a small hand gesture and Terach came in, sat at the table.

The players are in position,Kresh told himself.Let the games begin.

JOMAINE Terach felt lost in a jumble of emotions. He was confused, tired, frightened, angered, fearful, angry. He knew perfectly well he was in no fit state to be questioned. But that was exactly why they had chosen this moment to grill him.

Alvar Kresh grinned unpleasantly at him, and spoke in a voice that made it clear that he was enjoying himself. "Why don't I just save time and tell you what we already know?" he asked. " And maybe this time you can be just a little bit more forthcoming with your answers. That way I won't be tempted to use the charges we have against you already-the ones related to obstructing an investigation and failing to provide full and complete answers to a police officer. How does that sound to you?" Alvar Kresh smiled again, even more unpleasantly, as he looked his prisoner in the eye.

Jomaine Terach stared back and tried to keep calm, tried to calculate, tried to figure the situation. The night behind bars had been a long one, and it had not done his state of mind any good. No doubt it was not meant to. It was a fairly safe bet that they had picked up Gubber and maybe Fredda at the same time they got him. However, no one in the Sheriff's Department was admitting to that or much of anything else.

But if Gubber was in here, well, Gubber was not much given to calm in the face of adversity. A night in a cell was likely to make Gubber's tongue quite loose. And lurking in the background of Alvar Kresh's angry, threatening courtesy was the unspoken threat of the Psychic Probe. No sane man wished to facethat, and Jomaine regarded himself as eminently sane. Sane enough to know just how serious the charges against him could get if Kresh wanted to throw the book at him.

If he wanted to stay free and with a whole mind, he was going to have to tell Kresh what he wanted to know, and tell it to himbefore Gubber or Fredda did. The time had come to protect himself from everyone else's mad schemes. Unless that time was already past.

"Say what you have to say and ask your questions," he said. "I don't know it all. I didn'twant to know it all. But what I know, I'll tell you. I have run out of reasons for silence."

Alvar Kresh leaned back in his chair. "All right," he said. "Let me start by telling you part of what we know already, and just see how well you do filling in the blanks."

The operative word there waspart, of course, Jomaine told himself. Was Kresh going to tell ninety-five percent of what the police knew, or five percent? There were any number of traps and pitfalls here.

"We know for starters that Caliban is not a Three Law robot, not even one of these damned New Law robots, but a No Law robot."

Kresh looked hard at Jomaine, stared him down. The testing was starting early. Here was his chance, Jomaine realized. Kresh wanted to see what he would do if given the chance to play games. Kresh had not even asked a question. It was Jomaine's chance to ask what a No Law was, or who Caliban was.

But Jomaine had a pretty fair idea what would happen if he did that, and he had no desire to find out if he was right.

The silence went on for another few seconds before Jomaine Terach could bring himself to speak the words.

"Yes," he said. "Caliban is a No Law."

"I see," Kresh said. "How is that possible?"

Jomaine was thrown off balance by the question, and no doubt that was the intention. "I-I don't understand," he said. "What do you mean?"

"I believe that what the Sheriff wishes to know are the technical details of the process," Donald 111 said.

Jomaine looked over to the small blue robot, and was not fooled for a minute by Donald' s unprepossessing appearance and gentle voice. Donald had come out of Leving Labs, after all, and Jomaine had had a hand in his design. Behind that harmless blue exterior was a formidable mind, a positronic brain that came close to the theoretical limits for flexibility and learning ability.

"You mentioned in our first interview after the attack that gravitonic brains were a new departure," Kresh said, his voice deceptively mild.

"Yes, they are. Gubber designed them that way and was justifiably proud of what he had done. But no one would listen to him-until he came to Fredda."

"All right, that's fine. But then we get into a problem area. I am not very happy to hear about this New Law experiment, to say the least, but it appears to have legal sanction from the Governor, and I don't see that there is much I can do about it. But, as I understand it, these gravitonic brains have the New Laws as part of their integral makeup, just as the positronic brain' s basic structure must of necessity include the Three Laws. So how did you manage to erase those laws from Caliban's brain?"

"They were never there in the first place," Terach said. "Thereare no Laws inherent in the structure of the gravitonic brain. That's the whole idea. The positronic brain became a dead end precisely because the Three Laws were so tightly woven into it. Because of the inherent nature of the Laws inside the positronic brain, it was almost impossible to consider one element of the brain by itself.

"The Laws interconnected all the aspects of the brain so thoroughly that any attempt to modify one part of a positronic brain would affect every other part of it in complex and chaotic ways. Imagine that rearranging the furniture in your living room could cause the roof to catch fire, or the paint on the basement walls to change color, and that putting out the fire or repainting could cause the doors to falloff and the furniture to reset to its original configuration. The interior architecture of the positronic brain is just about that interconnected. In any sort of deep-core programming or redesign, anything beyond the most trivial sort of potential adjustment was hopelessly complex. By leaving the gravitonic brain with a clean structure, by deliberatelynot making the Three Laws integral to every pathway and neural net, it became far easier to program a new pattern onto a blank brain."

Jomaine looked up and saw the anger and disgust on Alvar Kresh's face. Clearly the very idea of tampering with the Three Laws was the depths of perversion so far as he was concerned. " All right," the Sheriff said, trying to keep his voice even. "But if there are no Laws built into the gravitonic brains, how do these damned New Laws get in there? Do you write them down on a piece of paper and hope that the robot thinks to read them over before going out to attack a few people?"

"No." Jomaine swallowed hard. "No, no, sir. There is nothing casual or superficial about the way a Law set-either Law set.:-is embedded into a gravitonic brain. The difference is that the lawset is embedded centrally, at key choke points of the brain's topology, if you will. It is embedded not just once, but many times, with elaborate redundancy, at each of these several hundred sites. The topology is rather complex, but suffice it to say that no cognitive or action-inductive processing can go on in a gravitonic brain without passing through a half dozen of these Law-support localities. The difference is that in a modern positronic brain, the Laws are written millions, even billions, of times, across the pseudocortex, just as there are billions of copies of your DNA written, one copy in each cell of your brain. The difference is that your brain can function fairly well if even a large number of cells are damaged, and your body will not break down if a few DNA cells fail to copy properly.

"In a positronic brain, the concept of redundancy is taken to an extreme. All of the copies must agree at all times, and the diagnostic systems run checks constantly. If a few, or even one, of the billions of redundant copies of the embedded Three Laws do not produce identical results compared to the majority state, that can force a partial, perhaps even a complete, shutdown." Jomaine could see in Kresh' s face that he was losing him.

"Forgive me," Jomaine said. "I did not mean to lecture at you. But it is the existence of these billions of copies of the Laws that is so crippling to positronic brain development. An experimental brain cannot reallybe experimental, because the moment it shifts into a nonstandard processing state, five billion microcopies of the Three Laws jump in to force it back into an approved mode."

"I see the difficulty," Donald said. "I must confess that I find the concept of a robot with your modified Three Laws rather distressing. But even so, I can see why your gravitonic brains do not have this inflexibility problem, because the Laws are not so widely distributed. But isn't it riskier to run with fewer backups and copies?"

"Yes, it is. But the degree of risk involved is microscopic. Statistically speaking, your brain, Donald, is not likely to have a major Three Laws programming failure for a quadrillion years. A gravitonic brain with only a few hundred levels of redundancy is likely to have a Law-level programming failure sooner than that. Probably it can't go more than a billion or two years between failures.

"Of course, either brain type will wear out in a few hundred years, or perhaps a few thousand at the outside, with special maintenance. Yes, the positronic brain is millions of times less likely to fail. But even if the chance of being sucked into a black hole is millions of times lower than the chance of being struck by a meteor, both are so unlikely that they might as well be impossible for all the difference it makes in our everyday lives. There is no increase in thepractical danger with a gravitonic brain."

"That is a comforting argument, Dr. Terach, but I cannot agree that the danger levels can be treated as equivalent. If you were to view the question in terms of a probability ballistics analysis-"

"All right, Donald," Kresh interrupted. "We can take it as read that nothing could be as safe as a positronic brain robot. But let's forget about theory here, Terach. You've told me how the New Laws or Three Laws can be embedded into a gravitonic brain. What about Caliban? What about your splendid No Law rogue robot? Did you just leave the embedding step out of the manufacturing process on his brain?"

"No, no. Nothing that simple. There are matrices of paths meant to contain the Laws, which stand astride all the volitional areas of the gravitonic brain. In effect, they make the connection between the brain' s subtopologic structures. If those matrices are left blank, the connections aren't complete and the robot would be incapable of action. Wecouldn't leave the matrices blank. Besides, there would be no point to it. Caliban was-was-an experiment. Never meant to leave the lab. Fredda was going to install a perimeter restriction device on him the night it, ah, happened. But he was powered up prematurely, before the restricter was installed."

"What, Doctor, was the nature of the experiment?" Donald asked.

"To find out what laws a robot would choose for itself. Fredda believed-we believed-that a robot given no other Law-level instruction than to seek after a correct system of living would end up reinventing her New Laws. Instead of laws, she-we-embedded Caliban ' s matrices with the desire, the need, for such laws. We gave him a very detailed, but carefully edited, on-board datastore that would serve as a source of information and experience to help him in guiding his actions. He was to be run through a series of laboratory situations and simulations that would force him to make choices. The results of those choices would gradually embed themselves in the Law matrices, and thus write themselves in as the product of his own action."

"Were you not at all concerned at the prospect of having a lawless robot in the labs?" Donald asked.

Jomaine nodded, conceding the point. "We knew there was a certain degree of risk to what we. were doing. We were very careful about designing the matrices, about the whole process. We even built a prototype before Caliban, a sessile testbed unit, and gave it to Gubber to test in a double-blind setup."

"Double-blind?" Kresh asked.

"Gubber did not know about the Caliban project. No one did, besides Fredda and myself. All Gubber knew was that we wanted him to display a series of situation simulations-essentially holographic versions of the same situations we wanted Caliban to confront-to the sessile free-matrix testbed unit, alongside a normally programmed Three Law sessile testbed. We would have preferred using a New Law robot, of course, because those were the Laws we wanted Caliban to come up with on his own. Unfortunately we hadn't received any sort of approval for lab tests of New Law robots at that point, so that was no go.

"But the main test was to see if an un-Lawed brain could absorb and lock down a Law set. Gubber did not know which was which, or even that the two were supposed to be different. Afterwards he performed a standard battery of tests on the two units and found that the results were essentially identical. The sessile No Law robot had absorbed and integrated the Three Laws, just as predicted."

"What happened to the testbed units?" Donald asked.

"The No Law, free-matrix unit was destroyed when the test was over. I suppose the Three Law unit was converted into a full robot and put to use somehow."

"What goes into converting a sessile unit?"

"Oh, that is quite simple. A sessile is basically a fully assembled robot, except that the legs are left off the torso while it is hooked to the test stand and the monitor instruments installed. Basically just plug the legs in and off it goes.

"At any rate, Fredda intended Caliban as a final grand demonstration that a rational robot would select her Laws as a guide for life."

"Wait a moment," Kresh said, rather sharply. "You're telling me this is what wassupposed to happen. Whatis happening? What is Caliban doing out there?"

Jomaine shrugged. "Who knows? In theory, he should be doing exactly what I've just described-using his experience to codify his own laws for living."

Kresh reached out his hands and placed them flat on the table, tapping his right index finger on its surface. He did not speak for half a minute, but when he did, all the masks were off. The calm, the courtesy, were gone, and only the anger remained in his steel-cold voice.

"In other words, this robot that assaulted and nearly killed its creator in its first moment of awakening, this robot that threw a man across a warehouse and committed arson and refused to follow orders and fled from repeated police searches-this robot is out there trying to find good rules forliving? Flaming devils, what, exactly, are the laws he has formulated so far? ' A robot shall savagely attack people, and will not, through inaction, prevent a person from being attacked?' "

Jomaine Terach closed his eyes and folded his hands in his lap.Let it be over. Let me wake up and know this is all a nightmare. "I do not know, Sheriff. I do not know what happened. I do not know what went wrong."

"Do you know who attacked Fredda Leving?"

"No, sir. No, I do not. But I cannot believe it was Caliban."

"And why is that? Every scrap of evidence points to him."

"Because I wrote his basal programming. He was not-is not-just a blank slate. He has no built-in Laws. Neither do you and I. But his innate personality is far more grounded in reason, in purpose, than any human ' s could be. You or I would be far more likely than he to lash out blindly in a random attack. And if I had made a mistake big enough to cause Caliban to attack Fredda like that, that mistake would have cascaded into every other part of his behavioral operant system. He would have seized up for good before he reached the door to the lab."

"Then who was it?"

"You have the access recorder records. Look there. It is some one of us on that list. That's all I can tell you for certain."

"Access recorder?"

Jomaine looked up in surprise. They hadn't known about the recorder! Of course. Why should they even think about such things? With the endless wealth of Spacer society, and the omnipresent robots to serve as watchkeepers, theft was almost unknown, and security systems even rarer. If he had not assumed they knew and let it slip, they never would have known. If he had kept his mouth shut about it, they would have had no way of knowing he had been at the lab that night, just about the time of the attack...

But it was too late to hold back. Now they would know what to ask about. There was nothing for it but to charge on. They would get the access records, and that would be that. "It's a Settler security device," he said. "Tonya Welton insisted that Fredda install it because Leving Labs had access to Limbo Project material. It records the date and time and identity of the person every time someone passes in or out of the lab. It works on a face-recognition system. Humans only. It was programmed to ignore robots. Too many of them."

Kresh turned toward Donald 111, but the robot spoke before the Sheriff had a chance. "I have already dispatched a technical team to the labs, sir. We should have the data from the access recorder within half an hour."

"Very good. Now, why don't you save us some time and effort, and tell us yourself whatever that recorder will tell us about your movements."

Jomaine was rattled. He had made a major mistake telling them about the recorder. But damnation! Now that they knew that much, there was no point in hiding anything else. "There is very little to tell. I had left a notepack in my lab. I noticed it when I sat down to get some work done at home. I live quite near the lab, and I walked over to collect it. I entered through the main door. I think I called out to see if anyone was around, and there was no answer. I went to my lab, got the notepack, and then left my lab by one of its side doors. That's all."

"That's your story."

"Yes, it is."

"Why didn't you send a robot to get the notepack?" Kresh said. "Seems to me like an errand suited to a robot."

"I suppose I could have sent Bertran, but that would have been more trouble than it was worth. I couldn't quite recall which notepack the data I wanted was in, or where I had left it. Sometimes I can't even recall which pack I need. I have to put my eyes on it to be sure. My lab is often a bit of a jumble, and there are notepacks all over the place. I find that if I just stand and look at a room for a minute, I remember where the thing I'm looking for is. A robot can't do that for me."

Jomaine had the uncomfortable sense that he was babbling, going on and on, but there seemed to be no way out but forward with more of the same. "Bertran would have brought me a half dozen notepacks to be sure I had the right one, which seemed a bit silly. I knew that I would be able to find the notepack myself the moment I stepped into the lab. And sure enough, I did."

"That seems like a rather overexplained set of reasons for why it was easier to do it yourself."

Jomaine glared at Kresh. "Yes, I suppose it does. But bear in mind that all of us down at Leving Labs have been hearing Fredda's theories about excessive dependence on robots for some time now. We've all developed a bit of a fetish about doing things for ourselves."

Kresh grunted. "I know how that can be," he said. " All right. You've filled in quite a few blanks for us, Terach. You're free to go-for now. But if I were you, I'd work on the assumption that you and I were going to have other little chats in future, about other questions that will come up. And the better your memory is when that happens, the better you and I will both like it. Do I make myself clear?"

Jomaine Terach looked Sheriff Alvar Kresh straight in the eye and nodded. "Oh, yes," he said. "There is nothing in the world clearer to me than that."

JOMAINE Terach stumbled out of Government Tower into the thin light of morning. He felt a pang of guilt for betraying Fredda' s confidence, but little more than that. What good were petty little secrets when a whole world was turning upside down in panic? The debts he owed to the good of society, and to himself, far outweighed his obligation to Fredda. Besides, you could not know. There might be some key to it all buried deep, hidden in his words where he could not even see it. Maybe Kresh could find that key and turn it in the lock. Maybe, just maybe, by talking, he had saved them all.

Jomaine snorted in disgust. High and mighty talk for a man who had spilled his guts. There was another explanation, one that did not come out quite so noble.

Maybe, just maybe, he was a coward at the heart.

He hailed an aircab and headed toward home.

"THE access recorder data, sir," Donald said, handing him a notepack.

"Thank you, Donald," Kresh said. He skimmed over the data once or twice, then studied it in greater detail. Damnation! Why hadn't he had this data days before? It provided him something he had not had until this moment-a nice, tidy list of suspects. Suspect humans, at least. Terach had said the thing did not record the comings and goings of robots.

"Sir, was it wise to let Jomaine Terach go free?" Donald asked. "I do not think we can consider his interrogation to be complete, and he did confess to several crimes related to violations of robot manufacture statutes."

"Hmmmm?" Kresh said absently. "Oh, Terach. It's a bit of a gamble, but if we want this case to get anywhere, I think we had to set him free-at least for now. And the same for Anshaw when we 're done with him. Neither of them has much of anyplace to go. I don't regard them as flight risks. But I'm counting on at least one of them panicking. If one or both of them does, it is damned likely they will make some sort of mistake, and it is likely that their mistakes could make our jobs a lot easier. Now go and bring Anshaw in."

"Yes, sir." Donald went through the door, down to the holding cells.

Alvar Kresh stood up and paced the interrogation room. He was eager, anxious. Things had shifted suddenly. He could not explain how, or why, exactly, but nonetheless they had. The access recorder data was part of it, but not all of it. All it did wassuggest certain things. It would be up to Kresh to prove them. He sensed that he was suddenly on the verge of answers, knocking on the door of a solution to this whole nightmare fiasco. All he had to do was press, push, bear down, and it would come.

Gubber Anshaw. Kresh dropped the notepack onto the table and thought about Anshaw. The interrogation that had been put off, delayed, pushed back, forgotten, lost in the chaotic shuffle of events again and again. And now, with the access recorder data in his hand, with the fact of Ariel ' s presence at Anshaw ' s home last night, it was suddenly clear thatthis was the interrogation that could break this case wide open. This was the man who knew things.

Alvar Kresh paced twice more up and down the room, but then forced himself to sit down and wait.

The door opened, and Donald ushered in Gubber Anshaw.

Alvar Kresh waited for Anshaw to sit down in the chair on the opposite side of the table. Then he set his hands palm-down on the table and leaned forward. Then he looked the robotics designer in the eye.

It was time for thereal investigation to begin.