THE blow smashed into her skull.

Fredda Leving's knees buckled. She dropped her tea mug. It fell to the floor and shattered in a splash of brown liquid. Fredda crumpled toward the ground. Her shoulder struck the floor, smashing into the broken shards of the cup. They slashed into her left shoulder and the left side of her face. Blood poured from the wounds.

She lay there, on her side, motionless, curled up in a ghoulish mockery of the fetal position.

For the briefest of moments, she regained consciousness. It might have been a split second after the attack, or two hours later, she could not say. But shesaw them, there was no doubt of that. She saw the feet, the two red metallic feet, not thirty centimeters from her face. She felt fear, astonishment, confusion. But then her pain and her injury closed over her again, and she knew nomore.

ROBOT CBN-001, also known as Caliban, awoke for the first time. In a world new to him, his eyes switched on to glow a deep and penetrating blue as he looked about his surroundings. He had no memory, no understanding to guide him. He knew nothing.

He looked down at himself and saw he was tall, his body metallic red. His left arm was half-raised. He was holding it straight out in front of him, his fist clenched. He flexed his elbow, opened his fist, and stared at his hand for a moment. He lowered his arm. He moved his head from side to side, seeing, hearing, thinking, with no recollection of experience to guide him.Where am I, who am I, what am I?

I am in a laboratory of some sort, I am Caliban, I am a robot.The answers came from inside him, but not from his mind.From an on-board datastore, he realized, and that knowledge likewise came from the datastore.So that is where answers come from, he concluded.

He looked down to the floor and saw a body lying on its side there, its head near his feet. It was the crumpled form of a young woman, a pool of blood growing around her head and the upper part of her body. Instantly he recognized the concepts ofwoman, young, blood, the answers flitting into his awareness almost before he could form the questions. Truly a remarkable device, this on-board datastore.

Who is she?Why does she lie there?What is wrong with her?He waited in vain for the answers to spring forth, but no explanation came to him. The store could not-or would not-help him with those questions. Some answers, it seemed, it would not give. Caliban knelt down, peered at the woman more closely, dipped a finger in the pool of blood. His thermocouple sensors revealed that it was already rapidly cooling, coagulating. The principle of blood clotting snapped into his mind.It should be sticky, he thought, and tested the notion, pressing his forefinger to his thumb and then pulling them apart.Yes, a slight resistance.

But blood, and an injured human. A strange sensation stole over him, as he knew there was some reaction, some intense, deep-rooted response that he should have-some response that was not there at all.

The blood was pooling around Caliban' s feet now. He rose to his full two-meter height again and found that he did not desire to stand in a pool of blood. He wished to leave this place for more pleasant surroundings. He stepped clear of the blood and saw an open doorway at the far end of the room. He had no goal, no purpose, no understanding, no memory. One direction was as good as another. Once he started moving, there was no reason to stop.

Caliban left the laboratory, wholly and utterly unaware that he was leaving a trail of bloody footprints behind. He went through the doorway and kept on going, out of the room, out of the building, out into the city.

SHERIFF'S Robot Donald DNL-111 surveyed the blood-splattered floor, grimly aware that, on all the Spacer worlds, only in the city of Hades on the planet of Inferno could a scene of such violence be reduced to a matter of routine.

But Inferno was different, which was of course the problem in the first place.

Here on Inferno it was happening more and more often. One human would attack another at night-it was nearly always night-and flee. A robot-it was nearly always a robot-would come across the crime scene and report it, then suffer a major cognitive dissonance breakdown, unable to cope with the direct, vivid, horrifying evidence of violence against a human being. Then the med-robots would rush in. The Sheriff's dispatch center would summon Donald, the Sheriff's personal robot, to the scene. If Donald judged the situation warranted Kresh' s attention, Donald instructed the household robot to waken Sheriff Alvar Kresh and suggest that he join Donald at the scene.

Tonight the dismal ritual would be played out in full. This attack, beyond question, required that the Sheriff investigate personally. The victim, after all, was Fredda Leving. Kresh must needs be summoned.

And so some other, subordinate robot would waken Kresh, dress him, and send him on his way here. That was unfortunate, as Kresh seemed to feel Donald was the only one who could do it properly. And when Alvar Kresh woke in a bad mood, he often flew his own aircar in order to work off his tension. Donald did not like the idea of his master flying himself in any circumstances. But the thought of Alvar Kresh in an evil mood, half -asleep, flying at night, was especially unpleasant.

But there was nothing Donald could do about all that, and a great deal to be done here. Donald was a short, almost rotund robot, painted a metallic shade of the Sheriff's Department's sky-blue and carefully designed to be an inconspicuous presence, the sort of robot that could not possibly disturb or upset or intimidate anyone. People responded better to an inquisitive police robot if it was not obtrusive. Donald's head and body were rounded, the sides and planes of his form flowing into each other in smooth curves. His arms and legs were short, and no effort had been made to put anything more than the merest sketch of a human face on the front of his head.

He had two blue-glowing eyes, and a speaker grille for a mouth, but otherwise his head was utterly featureless, expressionless.

Which was perhaps just as well, for had his face been mobile enough to do so, he would have been hard-pressed to formulate an expression appropriate to his reaction now. Donald was a police robot, relatively hardened to the idea of someone harming a human, but even he was having a great deal of trouble dealing withthis attack. He had not seen one this bad in a while. And he had never been in the position ofknowing the victim. And it was, after all, Fredda Leving herself who had built Donald, named Donald. Donald found that personal acquaintance with the victim only made his First Law tensions worse.

Fredda Leving was crumpled on the floor, her head in a pool of her own blood, two trails of bloody footprints leading from the scene in different directions, out two of the four doors to the room. There were no footprints leading in.

"Sir-sir-sir?" The robotic voice was raspy and rather crudely mechanical, spoken aloud rather than via hyperwave. Donald turned and looked at the speaker. It was the maintenance robot that had hyperwaved this one in.

"Yes, what it is?"

"Will she-will she-will she be all-all right right?" Donald looked down at the small tan robot. It was a DAA-BOR unit, not more than a meter and a half high. The word-stutter in his speech told him what he knew already. Before very much longer, this little robot was likely to be good for little more than the scrap heap, a victim of First Law dissonance.

Theory had it that a robot on the scene should be able to provide first aid, with the medical dispatch center ready to transmit any specialized medical knowledge that might be needed. But a serious head injury, with all the potential for brain damage, made that impossible. Even leaving aside the question of having surgical equipment in hand, this maintenance robot did not have the brain capacity, the fine motor skills, or the visual acuity needed to diagnose a head wound. The maintenance robot must have been caught in a classic First Law trap, knowing that Fredda Leving was badly injured, but knowing that any inexpert attempt to aid her could well injure her further. Caught between the injunction to do no harm and the command not to allow harm through inaction, the DAA-BOR's positronic brain must have been severely damaged as it oscillated back and forth between the demands for action and inaction.

"I believe that the medical robots have the situation well in hand, Daabor 5132," Donald replied. Perhaps some encouraging words from an authority figure like a high-end police robot might do some good, help stabilize the cognitive dissonance that was clearly disabling this robot. "I am certain that your prompt call for assistance helped to save her life. If you had not acted as you did, the medical team might well not have arrived in time."

"Thank thank thank you, sir. That is good to know."

"One thing puzzles me, however. Tell me, friend-where are all the other robots? Why are you the only one here? Where are the staff robots, and Madame Leving's personal robot?"

"Ordered-ordered away," the little robot answered, still struggling to get its speech under greater control. "Others ordered to leave area earlier in evening. They are in are in the other wing of the laboratory, And Madame Leving does not bring a personal robot with her to work."

Donald looked at the other robot in astonishment. Both statements were remarkable. That a leading roboticist did not keep a personal robot was incredible. No Spacer would venture out of the house without a personal robot in attendance. A citizen of Inferno would be far more likely to venture out stark naked than without a robot-and Inferno had a strong tradition of modesty, even among Spacer worlds.

But that was as nothing compared to the idea of the staff robots being ordered to leave. How could that be? Andwho ordered them to go? The assailant? It seemed an obvious conclusion. For the most fleeting of seconds, Donald hesitated. It was dangerous for this robot to answer such questions, given its fragile state of mind and diminished capacity. The additional conflicts between First and Second Laws could easily do irreparable harm. But no, it was necessary to ask the questions now. Daabor 5132 was likely to suffer a complete cognitive breakdown at any moment in any event, and this might be the only chance to ask. It would have been far better for a human, for Sheriff Kresh, to do the asking, but this robot could fail at any moment. Donald resolved to take the chance. "Who gave this order, friend? And how did you come to disobey that order?"

"Did not disobey! Was not present when order given. Sent-I was sent-on an errand. I came back after."

"Then how do you know the order was given?"

"Because it was given before! Other times!"

Other times?Donald was more and more amazed. "Who gave it? What other times? Who gave the order? Why did that person give the order?"

Daabor 5132's head jerked abruptly to one side. "Cannot say. Ordered not to tell. Ordered we were ordered not to say we were sent away, either-but now going away caused harm to human harm harm harm-"

And with a low strangling noise, Daabor 5132 froze up. Its green eyes flared bright for a moment and then went dark.

Donald stared sadly at what had been a reasoning being brief moments before. There could be no question that he had chosen rightly. Daabor 5132 would have failed within a few minutes in any event.

At least there was the hope that a skilled human roboticist could get further information out of the other staff robots.

Donald turned away from the ruined maintenance robot and turned his attention back toward the human victim on the floor, surrounded by the med-robots.

It was the sight that had destroyed the Daabor robot, but Donald knew he was, quite literally, made of sterner stuff. Fredda Leving herself had adjusted his First, Second, and Third Law potential with the express purpose of making him capable of performing police work.

Donald 111 stared at the scene before him, feeling the sort of First Law tension familiar to a sheriff's robot: Here was a human being in pain, in danger, and yet he could not act. The med-robots were here for that, and they could aid Fredda Leving far more competently than he ever could. Donald knew that, and restrained himself, but the First Law was quite clear and emphatic:A robot may not injure a human being, or, through inaction, allow a human being to come to harm. No loopholes, no exceptions.

But to aidthis human would be to interfere with the work of the med-robots, thus at least potentially bringingharm to Fredda Leving. Therefore, to do nothing was to aid her. But he was enjoined against doing nothing, and yet to aid her would be to interfere-Donald fought down the tremors inside his mind as his positronic brain dealt with the same dissonance that had destroyed Daabor 5132. Donald knew that his police-robot adjustments would see to it he survived the episode, as he had so many in the past, but that did not make it any less unpleasant.

Humans, on the other hand: These days, the sight of blood and violence scarcely bothered Alvar Kresh. Human beings could get used to such things. They could adapt. Donald knew that was so intellectually, he had observed it, but he could not understand how it was possible. To see a human in distress, in danger, to see a human as the victim of violence, even dead, and to be unmoved-that was simply beyond his comprehension.

But human or robot, the police saw a lot, especially on Inferno, and experience did make it easier in some ways. The paths of his positronic brain were well worn with the knowledge of how to deal with this situation, however disturbing that might be. Stay back. Observe. Gather data. Let the meds do their work.

And then wait for the human, wait for Alvar Kresh, wait for the Sheriff of the city of Hades.

The med-robots worked on the still form, rushing to stabilize her, ensure her blood supply, patching up the gashes in her shoulder and face, attaching monitor pads and drug infusers, moving her to a lift stretcher, shrouding her in blankets, inserting a breather tube into her mouth, cocooning her from sight behind their protections and ministrations.And that is how it should be, Donald thought.Robots are the shield between humans and the dangers of the world.

Though the shield had clearly failed this time. It was a miracle that Fredda Leving was even alive. By all appearances the attack had been remarkably violent. But who had done this, and why?

The observer robots hovered about, recording the images of this scene from every angle. Maybe their data would be of some use. Let them soak in all the details. Donald shifted his attention to the two sets of bloody footprints that led from the body. He had already tracked them out as far as they went. Both sets of prints faded away into invisibility after only a hundred meters or so, and he let it go at that. Police technical robots were already using molecular sniffers to try to extend the trails, but they wouldn't get anywhere. They never did.

But there was no missing the key fact, the vital piece of evidence. And no denying the horrible, unthinkable conclusion they suggested.

Both sets of footprints were robotic.Both sets. Donald, designed, programmed, trained in police work, could not avoid making the obvious and terrifying inference.

But it could not be. It couldn't be.

Donald devoutly wished for Alvar Kresh to arrive. Let a human take over, let someone who could get used to such things deal with the impossible thought that a robot could have struck Fredda Leving from behind.

THE night sky roared past Sheriff Alvar Kresh, and the scattered lights of buildings in Hades's outskirts gleamed bright below. He looked up into the dark sky and saw the bright stars glowing down at him. A beautiful night, a perfect night for a speed run over the city, something he only got the chance to do on official business, and he had to be in a foul mood.

He did not care for being awakened in the middle of the night, did not care for anyone but Donald helping him to dress.

He tried to cheer himself up, to soothe himself. He looked out into the night. Tonight was the best weather Hades had had in a long time. No sandstorms, no dust-haze. There was even a fresh tang of seawater blowing in off the Great Bay.

At least he could burn off his adrenaline and his anger by flying his aircar himself, rather than leaving the chore to a robot. He took a certain pride in that. Few humans even knew how to fly an aircar. Most people felt the chore of controlling an aircraft beneath them. They let the robots do it. No doubt most people thought it was damned odd that Alvar liked to fly his own car. But few people were likely to say that to the Sheriff's face.

Alvar Kresh yawned and blinked, and punched the coffee button on the aircar's beverage dispenser. He was alert, clear-eyed, but there was still a shroud of tiredness over him, and the first sip of the coffee was welcome. The aircar sped on through the night as he flew it one-handed, drinking his coffee. He grinned.Lucky Donald isn't here, he thought. It was stunts like flying one-handed that made it all but impossible for him to fly his own car when Donald, or indeed any robot, was on board. One false move and the robot would instantly leap into the copilot's seat and take over the craft's controls.

Ah, well. Maybe the Settlers sneered at robots, but no Spacer world could function for thirty seconds without them. That having been said, the damned things could be incredibly infuriating all the same.

Alvar Kresh forced himself to calmness. He had been roused from a sound sleep in the dead of night, and he knew from bitter experience that interrupted sleep made him more edgy than usual. He had learned long ago that he needed to do something to take the edge off himself when he was too keyed up, or else he was likely to take someone' s head off instead.

Alvar breathed the cool thin air. A nightflight over the desert at speed with the top open and the wind howling through his thick thatch of white hair helped drain away some of his temper, his tension.

But crimes of violence were still rare enough in Hades for him to take them personally, to get angry and stay that way. He needed that anger. This savage and cowardly attack on a leading scientist was intolerable. Maybe he did not agree with Fredda Leving's politics, but he knew better than most that neither the Spacer worlds in general nor Inferno in particular could afford the loss of any talented individual.

Alvar Kresh watched as the city swept by below him, and began to slow the aircar. There. The aircar's navigation system reported that they were directly over the Leving Robotics Labs. Alvar peered over the edge of the car, but it was difficult to get a fix on the precise building at night. He eased the car to a halt, adjusted its position over the landscape slightly, and brought it down to the ground.

A robot ground attendant hurried over to the car and opened the door for him. Alvar Kresh stood up and stepped out of the car, into the night.

There was a busy rummaging-about going on. A red and white ambulance aircar squatted on the ground near Kresh's car, its lift motors idling, its running lights on, obviously ready to lift off the moment its patient was aboard. A squad of med-robots bustled through the main door of the lab, two of them carrying a stretcher, the others holding feed lines and monitoring equipment hooked up to the patient. Leving herself was not quite visible under the tangle of life-support gear. A human doctor lounged by the hatch of the ambulance, watching the robots do the work. Alvar stood still and let the robots pass as they carried the victim from the scene of the crime.

He watched, his anger rising inside him, as the meds carried her into their van, and watched as the indolent human doctor eased his way into the ambulance behind his busy charges.How could anyone commit such violence against another human being? he asked himself.

But raw, unchanneled anger would not help catch Fredda Leving's assailant.Remain calm, he thought.Keep your anger controlled, focused. Alvar Kresh lifted his hand to a med-robot that was carrying a first-aid kit back to the ambulance. "What is the condition of your patient?" he asked.

The gleaming red and white med-robot regarded Kresh through glowing orange eyes. "She received a severe head injury, but no irreparable trauma," it said.

"Were her injuries life-threatening?" Kresh asked.

"Had we been delayed in reaching Madame Leving, her injuries could easily have been fatal," the robot said, a bit primly.

"However, she should recover completely, though there is the distinct possibility that she will suffer traumatic amnesia. We shall place her in a regeneration unit as soon as we reach the hospital."

"Very good," Kresh said. "You may go." He turned and watched the last of the med team climb into the ambulance and take off into the night. Good that she would recover, but it could be very bad indeed if she did suffer amnesia. People with holes in their memories made for bad witnesses. But the words of the med-robots changed the nature of the case.Her injuries could easily have been fatal. That changed a simple assault with a deadly weapon case into one of attempted murder. At last he turned to go inside the building, to see what Donald and his forensic team had come up with.