It was strange to see it all this way, from this godlike angle, but it was a remarkably useful way to sort out the movements of this person and that. Stranger still to see her own image and eliminate it, to see Alvar Kresh and make him vanish. It made her doubt his reality-and her own.

But should she make Alvar vanish? After all, he was the one who found the body. That in and of itself was a trifle suspicious. Donald had been a few steps behind him at the time. Kresh had not been alone in Grieg’s room for long, but suppose it had been for long enough-and even though it was a point open to interpretation, you could read the fact that Grieg had offered no struggle as a hint that he had been killed by someone he knew…

It seemed absurd-and yet someone had killed Grieg, and as of right now the rest of the universe only had Kresh’s word for it that he had found Grieg dead.

No. It couldn’t be. Not Kresh. The man might be stubborn and infuriating as hell, but there was no more honorable man on the planet. It was absurd to think that a man of his character could have done it. She knew him too well to believe such things. She was reluctant to admit such a thing, even to herself, but she liked him too well to believe such a thing.

Fredda glanced at Donald, seated impassively at the integrator’s control panel. Did fretful, disturbing thoughts like that flit through his mind? Was he troubled by such delusional nonsense? She, Fredda, ought to know. She had, after all, designed his brain, his mind, herself. But that meant nothing at a time like this. The short, sky-blue robot seemed unflappable-but what lurked under the surface? Was he intelligent enough to have doubts, to see that the universe was not the well-ordered, every-peg-in-its-proper-hole place that the Three Laws would make it seem? He was a police robot, after all, and knew as well as any robot in existence what sort of madness humans were capable of.

“Who do you think did it, Donald?” she asked, more or less on impulse. “Who killed Chanto Grieg?”

Donald had been watching the image playback, but now he turned toward Fredda and regarded her with an unreadable stare for a full ten seconds before he replied. “It is impossible for me to say,” he replied. “There is so much information already in our hands, and yet so little of it appears to be useful data. We are forced to eliminate meaningless information as a first step toward the truth. ”

“But you are more familiar with the case data than anyone. I know you suspect Caliban and Prospero, but leave them to one side for a moment. Who is your prime human suspect?”

Donald swiveled his head back and forth in an imitation of the human gesture of shaking his head to report uncertainty., ‘I am afraid I do not, and cannot, have an opinion on that. Before I could get to who, I would have to deal with why, to the question of motive. And I am simply incapable of imagining anyone wishing the-the death of a human being. I have seen death, I have witnessed the evidence of murder. I know there must, therefore, be motives for murder. But even though I know such things are real, I still cannot imagine them. ”

“Hmmph. Strange,” Fredda said. “Very strange. Humans are certainly capable of all sorts of remarkable delusions-but not that particular one. Sometimes I forget just how different robots are from humans. ”

“I don’t think I have ever forgotten that fact, even for a moment,” Donald said. “Shall we return to the task at hand?”

“Hmmm? Yes, of course. ” Fredda turned back to the integrator and watched the silent dance of the simulacra. They could have put sound in, of course, but that would do little more than add to the confusion at this point.

Wait a second. Confusion. Confusion. They were missing the point of all the confusion. “Donald. Go to the time reference five minutes before the attack on Tonya Welton-and delete Tonya Weltlon, the attackers, the SSS intervention, along with all the people we’ve identified so far. Let’s get rid of the diversion and see if we can spot what they were trying to divert us from. ”

“Yes, ma’am,” Donald said, manipulating the controls. He reset the system once again, running back to the proper moment in time. The image reappeared, affording the strange sight of all the bystanders reacting to the fight that was not happening. It was like watching an audience without being able to see the play. The little clumps of people turned and pointed at nothing at all in the center of the room, scuttled backwards to avoid the brawlers who were not there.

Fredda pointed at two or three of the largest groups of bystanders. They were clearly the ones being diverted, no sense in watching them. “Get rid of those people there,” she said.,, And those, and those. “ People vanished wholesale. Fredda let the sequence keep going. The fight had drawn people into the room from other parts of the Residence-but she was looking for the people who weren’t drawn by the noise. Fredda watched until the crowds gathered, had watched the now nonexistent action, and had begun to drift away.

“Freeze it there, Donald. Mark on those people-those, and those. And that clump over by the door. All right now. Now-backtrack to five minutes before the fight, and delete all of the people just marked from the image trail. I only want to see the ones who weren’t drawn to the fight.”

The 3-D image blanked for a moment, then came back up on the same scene minutes before the attack. There was no one left in the Grand Hall except Caliban and Prospero. Donald was showing his prejudices again. Both Caliban and Prospero had been in sight of one video camera or another throughout the entire evening, and beyond breaking up the fight, neither of them had done anything more suspicious than chat politely with the other guests. That, clearly, was not enough to satisfy Donald. But she let it go.

After all, there was the bare possibility that he was even right to suspect them. They had Verick’s statement that the two robots were the last ones to see Grieg alive.

But never mind that now. Fredda knew all about Prospero and Caliban. She was looking for unknowns, people she could not account for. “Give me an overhead view of the ground floor,” Fredda said. The image of the Grand Hall vanished, to be replaced by a cutaway view of the entire lower level, presented so Fredda was looking straight down on it from overhead. “Good,” she said. “Have you got all our personnel deletions saved for recall?”

“Yes, Dr. Leving. Shall I run the deleted-persons sequence forward from the same time mark before the fight?”

“In a minute, Donald. First, I want you to run it from that time with everyone still in place. Let’s see the whole picture first. ”

“Yes, ma’am.”

The images cleared.

The 3-D image blanked for a moment, then suddenly Fredda was looking down on an eddying throng of people, talking, walking, sitting, arriving, departing, arguing, laughing. It seemed as if the entire Residence were filled with people who desired nothing more than to be somewhere they were not. Everyone was on the move. It would be almost impossible to track anyone person in all of that. Which was, no doubt, what the conspirators were counting on.

The fight started, and Fredda found that her eye was pulled toward it. People hurried in from all directions to see what was going on, and it was almost impossible to see what anyone person was doing from moment to moment.

The two men attacked Tonya Welton; she knocked one of them down, and was about to rush the second when the two robots stepped in and pulled them apart. Kresh and Donald appeared, and Kresh waded in to sort things out. The crowd started to disperse just a little as the excitement came to an end.

“All right, Donald,” Fredda said. “Stop. Reset to the previous time index and run it again, with all the personnel deletions.”

Donald stopped the playback and reset the system. The vision tank dissolved in a swirl of colors and then reassembled itself to show a ghostly, empty house, with but a few faceless creatures wandering the building. They were constructs, place holders to indicate unidentified people, their faces too blurry for computer or robot or human to know who they were. No doubt most or even all of them could be identified with a bit more work, but that could wait. For now they were ghosts, ghosts in the machine, faceless beings walking through a simulated landscape. Some of them vanished or reappeared now and again as they were spotted and then lost by this or that video source. Sometimes, but not always, the integrator would connect two video sequences of the same person up with animated links.