The air underground was stale and hot, redolent of train-grease, electricity, sweat, fried food, piss-wet newspapers. The platform was more crowded than the murderer-to-be had anticipated. He had not known of a new play in the neighborhood, whose audience now spilled out and down into the subway. Such events were outside his calculus, and he would have still been baffled, had it not been or the overheard chance comments of the crowd.

The man felt uneasy. But he finally resolved to carry out his plans.

Necessity--and something resembling pride in his illicit trade--compelled him.

His roving eyes finally settled on a victim: a middle-aged woman in a fur coat, seemingly unaccompanied, clutching a strapless evening purse. He began to move toward her in a seemingly aimless yet underlyingly purposeful path.

The rumble and screech of an approaching train emerged from some distance down the tunnel. People surged closer to the edge of the platform in anticipation.

The man came up behind his apparently unaware victim, within reach of the shiny black purse clutched against her side.

Then it was in his hands. He tugged and pivoted.

The purse did not come. A thin hidden gold chain was looped around the woman's wrist.

He yanked, she screamed and flailed. He grabbed her wrist to immobilize it so that he could get the bag off. She jerked backward at the touch, the chain parted, his grip slipped, and the woman tumbled out of sight, onto the tracks.

The man turned to flee, but was brought crashingly down within a few yards by two bystanders, large men who began to pound him, smash him with their fists to stop his instinctive resistance.

And because his battered face was pressed into the filthy concrete at the moment he became a murderer, he did not see the train actually kill the woman.

But he heard and would always remember the noise of its useless brakes and the shouts of the witnesses and the victim's final cut-off high piercing scream.

"We think we have some chance of success with you," said the head of the Renormalization Board, as he looked up from closing a window on his lap-top, a window full of information on the nameless man. "But everything depends on your attitude. You will have to work at this, perhaps harder than you've ever worked at anything before. Your reintegration into society will not be without obstacles or sacrifices. Do you think you can commit to this course of action? Honestly, without reservations?"

Sitting across a wide polished table from the Board, the murderer tried to hide his astonishment and suspicion, keep it from altering the silent stony lines of his face. After six months on Death Row, his appeals up to and including the highest court exhausted in the streamlined new postmillennial system, with imminent and certain death staring him hourly in the face, he would agree to anything. Surely they knew that. Anything they could offer, even a life sentence, would be better than the alternative. And as he so far dimly understood the choice before him, it was infinitely more attractive than spending the rest of his natural days behind bars.

But after he said the assuring words these new judges wanted to hear and the Board began to explain exactly what lay in store for him, he began to have his first small trepidations.

"The first thing we are going to do is perhaps the most dramatic, yet surprisingly, not the most crucial. We are going to lift the top of your skull off and insert a little helper.

"Your cortex will be overlaid with a living mass of paraneurons known as an Ethical Glial Assistant, which will also have dendritic connections to various subsystems in your brain. This ECA has no independent capacities of its own, and assuredly no personality, no emotional or intellectual traits. You may think of it simply as a living switch. It has one function, and one function only. It will monitor aggressive impulses in your brain. Upon reaching a certain threshold--a threshold of whose approach you will be amply warned by various unpleasant bodily sensations--it will simply shut you down. You will go unconscious, and remain so for a period varying from half an hour to a day, depending on the severity of the attack.

"At this point, we would like to stress all the things the EGA will not do. It will not prevent you from physically defending yourself under most circumstances, although some incidents of this sort might very well pass into an aggressive stage and trigger the switch. It will not hinder your free will in any manner. You are always at liberty to attempt aggression; it is just that you must be willing to face the consequences." The Boardmember's voice became very dry. "We can report that most people's automobile driving styles change radically. In any case, we have no interest in turning you into some kind of clockwork human. You would be of little use to society and the planet that way. The SCA is by no means foolproof. It will certainly not thwart a coolly premeditated murder for profit. It works only on spontaneous limbic impulses of rage and attack.

"But we do not feel, based on your case history, that you are at risk of the more calculated life-threatening behavior. The antidote we are giving you is precisely tailored for the type of person you are. Or once showed yourself to be. With the help of the EGA, you will be rendered relatively safe to mingle with your fellow humans. As safe, in fact, as any of them generally are themselves. Do you understand all this so far?"

The murderer could not focus on anything other than the queasy image of his head being opened and a living mass of jelly dropped in. But then the picture of his cell and its proximity to the execution chambers returned.

"Yes," he said.

"Good, good. Now, we are not going to rely entirely on the ECA. It is, in its way, a last-ditch defense. You are going to undergo an intensive course of remedial psychosocial pragmatics. At the end of that time, if you have exhibited cooperation and commitment, you will be certified a fully functional member of society."

The prisoner could contain the question no longer. "And then, I'll be released? Free?"

The Boardmember smiled wryly. "In a manner of speaking, yes. Completely free. Yet with duties. The duties any of us here might have, to our society and the globe. You'll receive a brochure that explains it all. It's quite simple, really."

The head of the Renormalization Board now opened up a scheduling window on his computer. "Let me see . . . Assuming you can complete the standard six-month course, and that Mr. Swan survives till then in order to serve as your surrogate--Yes, I think that we can confidently schedule your execution for the fifteenth of May. How does that sound to you?"

"Fine. Uh, fine."