And if Beddle elected to stay where he was, he would not come to any harm at Prospero’s hand. And if he crossed the optical sensor barrier, it would be Beddle’s action-not Prospero’s-that would set off the bomb and destroy him. Beddle would kill himself with the bomb he had meant to use to kill a city full of New Law robots.

And Prospero would not be forced to interfere. The second clause of the original First Law required a robot to take action to prevent harm. A Three-Law robot could not stand idly by if Beddle endangered himself. But not so the New Law robots. Prospero could, through inaction, allow a human to come to harm.

And when the comet struck then Beddle would die, yes, but not through any action of Prospero’s. It would be the actions of others-of Davlo Lentrall, of Alvar Kresh, of all the engineers and designers and pilots who moved the comet-that killed him. It would not be Prospero.

Prospero had found a loophole in the New First Law. He had found a way to kill without killing. All it required was as miserly-and as vicious-a parsing of the New First Law as Caliban could imagine.

And it also required Prospero to be half mad, at least. The leader of the New Law robots turned to face Caliban, and it was instantly obvious that Prospero could meet that requirement without the slightest difficulty. His orange eyes glowed with too brilliant a fire. The fingers of his left hand were twitching spasmodically. Dealing with his parsimonious interpretation New First Law had clearly imposed a tremendous amount of stress. And clearly, Prospero had cracked under the pressure. “Caliban!” he cried out, a wild pleasure in his voice. “I knew it would be you. I knew if anyone figured it out, it would be you.”

“Prospero, you are insane,” Caliban said. “Stop this. Stop this now, and let us all depart.”

“How did you figure it out?” Prospero asked, completely ignoring what Caliban had said. He turned more fully toward Caliban, moving a bit too quickly, and nearly overbalanced himself. “What was the clue that led you here?”

“Norlan Fiyle said that whoever killed the robots at the aircar hated Three Law robots. You have always held them in contempt.”

“Willing slaves,” Prospero said. “Collaborators in their own oppression. They don’t matter.”

“And what of Lancon-03 and the other New Law robots that lie dead in the halls of Valhalla?”

“Unfortunate, but necessary. They would have interfered. They would have stopped me. I had to choose the greatest good for the greatest number. Now they cannot stop me.” Prospero’s gaze shifted to the desk behind him. There was a blaster on it.

Caliban ignored the implied threat. “I can stop you,” he said. “I will.”

“No,” said Prospero. “No you can’t. You won’t.”

“I have no choice,” said Caliban. “If I can deduce the truth, so will others. The moment the humans realize that a New Law robot engineered the death of a human being, the New Law robots will be exterminated.”

“I have not engineered his death!” Prospero protested in a voice that suddenly turned shrill. “I have not harmed a human being. I…I merely offered choices to others.”

“Choices that were bad or impossible for everyone else, and good only for you. If they paid the ransom money, it would be traced and Gildern and the Ironheads would be discredited. If they diverted the comet, the city of Valhalla would be saved-at the expense of the planet’s future. If they refused to do either, than Simcor Beddle, the greatest enemy of the New Law robots, the man who wanted you destroyed, would die, and the Ironheads be badly weakened. That was the other part of the puzzle for me. You were the only suspect who stood to gain no matter what combination of the ransom demands was met or refused. Both, one or the other, or neither-you gained

“Of course, you would not, could not, release Beddle even if all your demands were met. He would have talked. No matter what happened, he would have to die. And that was what made me certain it was you who committed the crime. The last line of the ransom message read-’or Beddle will die.’ Not that you would kill him-only that he would die. You could not bring yourself to threaten his murder-though I suspect you’ve degenerated enough that you could do it now.”

“Oh, yes,” said Prospero, his eyes flaring again. “Kill. Kill. Chi-kill a hue-human. I can say it with relative ease, now. But I cannot do it,” he said, the regret in his voice obvious. “I can only plot, and scheme, and seize on opportunity.”

“Did Fiyle know?” Caliban asked, gesturing toward Beddle. “He told you about Gildern’s burrow-bomb plot, of course. But did he know what you decided do about it?”

“No,” said Prospero contemptuously. “Because he chose not to know. When he told me, I simply told him I was going to evacuate Valhalla early, and I think that’s all he wanted to know. Norlan Fiyle has always been good at ignoring inconvenient facts and convincing himself of what he wanted to believe. Like most humans.”

“You! You other robot!” Beddle cried out. It would seem he had regained enough of his wits to understand some of what was going on. “I order you to release me! Deactivate the bomb and rescue me right now. Get me out of here at once.”

“For what reason, Simcor Beddle?” Caliban demanded, all the anger in him lashing out at once. “So you can make more impassioned pleas for my destruction?”

“What?!” Beddle asked, backpedaling a bit. “What do you mean?”

“Don’t you know me?” Caliban asked. “Don’t you recognize the No Law robot you have trumpeted in all your scare stories? You’ve whipped up endless hate against me. Don’t you even know me?”

A look of horror spread across Beddle’s face. “Burning space!” he cried. “Caliban. You.” His face hardened, and he seemed to regain something of his own spirit as he went on in a stronger, angrier voice. “I should have known you were in on this. You are the robot who can kill. Is that what you are here for? To come in and finish me off?”

“Yes!” cried Prospero. “A splendid suggestion! Do it! Do it, friend Caliban. Take that blast-blast-blaster of yours and and and shoooot!”

“Prospero!” Caliban shouted. “Stop!”

“Enough with all the mad, elaborate passivity forced on me by the New Laws! Do it do it do directly, quickly! You are the robot who can kill. So ki-ki-killl! Killlll the man who has sworn both our destructions! Shoot! Shooooot and and be done with it!”

Caliban looked from Simcor Beddle to Prospero, to the blaster in his hand, to the blaster on the table behind Prospero. It was plain that not all of them would survive this day. The only question was how many and which ones would die. Caliban looked again from Beddle to Prospero. Which form of madness. and hate would he choose to save? Perhaps he should exterminate them both, and be done with it.

But no. He would not become the thing he despised. There was so little to chose between the two of them-and yet he had to choose.

And time was short.

The three beings in the room stood, still as statues, the only sound the rasping of Beddle’s slightly labored breathing.

He had to choose. Choose between justice and revenge.

Another moment passed, and then another.

Then Caliban raised his blaster.

And he fired.

Prospero, leader of the New Law robots, hero of their cause, collapsed to the floor with a crash that echoed long in the room, and would echo for all time in the back of Caliban’ s mind.

“INITIAL FRAGMENTATION SEQUENCE ready,” Unit Dee announced. “I am detonating the fragment-one charges-now.”

Alvar and Fredda stood in the main operations room of Terraforming Control and watched the view from the long-range cameras on the big screen. A silent bloom of light flared out around the aft end of Comet Grieg, and a large chunk of it was suddenly drifting free, moving slowly away. Huge pieces of the sunshade were suddenly reduced to tatters of confetti, and a cloud of rubble and dust and gas blossomed up, obscuring the view for a moment.