The crowd thinned here as the step-down walk rounded a comer into a byway canyon between two towering windowless buildings. There was dust in this cavernous street rising up and almost concealing a distant tracery of bridges. Potter wondered at the dust. It was as though the director of local weather allowed dust here in an unconscious passion of naturalness.

A bulky man hurried past them and Potter was caught by the look of his hands - thick wrists, bulging knuckles, horned callouses. He had no idea what work could cause such deformity.

The guide steered them now onto a succession of drop walks and into the cave of an alley. The swarm was left behind. A feeling of detachment seized Potter. He felt he was re- living an old and familiar experience.

Why did I come with this person? he wondered. The guide wore the wheeled blazon of a transport driver on his shoulder, but he'd said right out he was from the Parents Underground.

'I know what you did for us,' he'd said. 'Now, we will do something for you.' A turn of the head. 'Come.'

They'd talked only briefly after that, but Potter had known from the first the guide had correctly identified himself. This was no trick.

Then why did I accept the invitation? Potter asked himself. Certainly it wasn't for the veiled promises of extended life and instant knowledge. There were Cyborgs behind this, of course, and he suspected this guide might be one of them. Most of the Optimen and Servant Uppers tended to discount the Folk rumors that Cyborgs did exist, but Potter had never joined the cynics and scoffers. He could no more explain why than he could explain his presence here in this alley cave walking between dark plasmeld walls illuminated by the ghost flicker of overhead glowtubes.

Potter suspected he had at last rebelled against one of the three curses of their age - moderation, drugs and alcohol. Narco-pleasures and alcohol had tempted him in their time... and finally moderation. He knew it wasn't normal for the times. Better to take up with one of the wild sex cults. But pointless sex without even the faint hope of issue had palled on him, although he knew this for a sign of final dissolution.

The alley opened into one of the lost squares of the megalopolis - a triangular paving and fountain that looked to be real stone, green with the slime of ages.

The Optimen don't know about this place. Potter thought They despised stone which eroded and wore away - in their time. Regenerative plasmeld was the thing. It stood unmoved and unmoving for all time.

The guide slowed as they reached the open air. Potter noted a faint smell of chemicals about the man, oily sweetness, and a tiny scar running diagonally down the back of his neck into his collar.

Why didn't he try to blackmail me into coming? Potter wondered. Could he be that sure? Could anyone know me that well?

'We have a job for you,' the guide had said. 'An operation you must perform.'

Curiosity is my weakness. Potter thought. That's why I'm here.

The guide put a hand on Potter's arm, said, 'Stop. Wait without moving.'

The tone was conversational, calm, but Potter felt hidden tensions. He looked up and around. The buildings were window-less, faceless. A wide door stood out in the angle of another alleyway ahead. They had come almost around the fountain without encountering another person. Nothing stirred or moved around them. There was only the faint rumbling of distant machinery.

'What is it?' Potter whispered. 'Why're we waiting?'

'Nothing,' the guide said. 'Wait.'

Potter thrugged.

His mind veered back to the first encounter with this creature. How could they know what I achieved with that embryo? It must be the computer nurse. She's one of them.

The guide had refused to say. came because I hoped they could help me solve the mystery of the Durant embryo, he thought. They were the source of the arginine intrusion - that's what I suspect.

He thought of Svengaard's description - a contrail-like intrusion. It had deposited arginine-rich sperm protamine through the coiled alpha-helices of the embryo's cells. Then had come the operation - the cysteine masked, neutralized with sulfhydryl and the ATP phase... oligomycin and azide... the exchange reaction inhibited.

Potter stared up at the patch of blue sky framed by the buildings around the square. His mind, concentrated on the Durant cutting, had encountered a new idea. He no longer saw the sky. His awareness was back within the swarming cell structure, following the mitochondrial systems like an undersea hunter.

'It could be repeated,' Potter whispered.

'Silence,' the guide hissed.

Potter nodded. On any embryo at all. he thought. The key's the a gmine flooding. I could duplicate that myself on the basis of Sven's description. Gods! We could make billions of Durant embryos! And every one of them self-viable!

He took a deep breath, dismayed by the realization that -with the record tape erased - his memory might be the only container of that entire operation and its implications. Sven- gaard and the computer nurse could have only part of it. They hadn't been in there, immersed in the heart of the cell.

A brilliant surgeon might deduce what had happened and be able to reproduce the operation from the partial records, but only if he were set the problem. Who would ever take up this problem? Not the Optimen. Not that dolt Svengaard.

The guide tugged at Potter's arm.

Potter looked down into that flat, chill-eyed face with its lack of genetic identification.

'We are observed,' the guide said in an oddly depersonalized tone. 'Listen to me very carefully. Your life depends on it.'

Potter shook his head, blinked. He felt removed from his own person, become only a set of senses to record this man's words and actions.

'You will go through that door ahead of us,' the guide said.

Potter turned, looked at the door. Two men carrying paper-wrapped parcels emerged from the alley in front of it, hurried around the square opposite them. The guide ignored them. Potter heard a babble of young voices growing louder in the alley. The guide ignored these, too.

'Inside that building, you will take the first door on your left,' he said. 'You will see a woman there operating a voicebox. You will say to her: 'My shoe pinches.' She will say: 'Everyone has troubles.' She will take care of you from there.'

Potter found his voice: 'What if... she's not there?'

Then go through the door behind her desk and out through the adjoining office into a rear hall. Turn left and go to the rear of the building. You will find there a man in a loader supervisor's uniform, striped gray and black. You will repeat the procedure with him.'

'What about you?' Potter asked.

'That is not your concern. Quickly, now!' The guide gave him a push.

Potter stumbled towards the door just as a woman in a teacher's uniform emerged from the alley leading a file of children between him and the bolt hole.

Potter's shocked senses took in the scene - children, all dressed in tight shorts that revealed their long flamingo legs. They were all around him suddenly and he was bulling his way through toward the door.

Behind him, someone screamed.

Potter lurched against the door, found the handle, looked back.

His guide had gone around to the opposite side of the fountain which concealed him now from the waist down, but what remained visible was enough to make Potter gasp and freeze. The man's chest was bare revealing a single milky white dome from which blazed a searing light.

Potter turned left, saw a line of men emerging from another alley to be crisped and burned down by that searing light. The children were shouting, crying, falling back into the alley from which they had emerged, but Potter ignored them, fascinated by this slaughter- machine which he'd thought was a human being.

One of the guide's arms lifted, pointed overhead. From the extended fingers, lancets of searing blue stabbed upward. Where the light terminated, aircars tumbled from the sky. The air all around had become an ozone-crackling inferno punctuated by explosions, screams, hoarse shouts.

Potter stood there watching, unable to move, forgetful of his instructions on the door or his hand upon the door's handle.

Return fire was coming now at the guide. His clothing shriveled, vanished in smoke to reveal an armored body with muscles that had to be plasmeld fibers. The ravening beams continued to blaze from his hands and chest.

Potter found he no longer could bear to watch. He wrenched the door open, stumbled through into the relative gloom of a yellow-walled foyer. He slammed the door behind him as an explosion rocked the building. The door rattled behind him.

On his left, a door was flung open. A tiny blue-eyed blonde woman stood there staring at him. Potter found himself oddly recognizing the markers of her genetic cut, reassured by the touch of humanity in these tiny betrayals. He could see the cabinet of a voicebox in the room behind her.

'My shoe pinches,' Potter said.

She gulped. 'Everyone has troubles.'

'I am Dr Potter,' he said. 'I think my escort has just been killed.'

She stepped aside, said, 'In here.'

Potter lurched past her into an office with lines of empty desk. His mind was a turmoil. He felt shaken to his roots by the implications of the violence he had just witnessed.

The woman took his arm, herded him toward another door. 'Through here,' she said. 'We'll have to go into the service tubes. That's the only way. They'll have this place surrounded in minutes.'

Potter stopped, figuratively dug in his heels. He hadn't counted on violence. He didn't know what he had expected, but not that.

'Where're we going?' he demanded. 'Why do you want me?'

'Don't you know?' she asked.

'He... never said.'

'Everything'U be explained,' she said. 'Hurry.'

'I don't move a millimeter until you tell me,' he said.

A raw street oath escaped her lips. She said, 'If I must I must. You're to implant the Durant embryo in its mother. It's the only way we can get it out of here.' In the mother?' 'In the ancient way,' she said. 'I know it's disgusting, but it's the only way. Now, hurry!' Potter allowed himself to be herded through the door. Eleven

IN the control center, their red Survey Globe, the Tuyere occupied the thrones on the pivoting triangle, reviewing data and reviewing data - correlating, deducing, commanding. The 120-degree scan of curved wall available to each of them flashed with data in numerous modes - pictorially in the spying screens, as probability function in mathematical read-outs, as depth-module decision analogues, as superiorinferior unit apportionments pictured in free-flowing pyramids, as visual reports reduced to cubed grids of binaries according to relative values, as motivational curves weighted for actionreaction and presented in flowing green lines...

In the upper quadrants, scanner eyes glittered to show how many of the Optimen were sitting in on the globe's activity -over a thousand this morning.

Calapine worried the prescription ring on her left thumb, felt the abortive hum of power in it as she twisted and slid it along her skin. She was restless, full of demands for which she could find no names. The duties of the globe were becoming repellent, her companions hateful. In here, time settled into more of a continuous blur without days or nights. Every companion she had ever known grew to be the same companion, merged, endlessly merged.

'Once more have I studied the protein synthesis tape on the Durant embryo,' Nourse said. He glanced at Calapine in the reflector beside his head, drummed the arm of his throne with fingers that moved back and forth, back and forth on the carved plasmeld.

'Something we've missed, something we've missed,' Calapine mocked. She looked at Schruille, caught him rubbing his hands along his robe at his thighs, a motion that seemed filled with stark betrayal of nervousness.

'Now it happens I've discovered the thing we missed,' Nourse said.

A movement of Schruille's head caught Nourse's attention. He turned. For a moment, they stared at each other in the prisms. Nourse found it interesting that Schruille betrayed a tiny skin blemish beside his nose.

Odd, Nourse thought. How could one of us have a blemish such as that? Surely there could be no emymic imbalance.

'Well, what is it?' Schruille demanded.

'You've a blemish beside your nose,' Nourse said.

Schruille stared at him.

'You deduce this from the embryo's tape?' Calapine asked.

'Eh? Oh... no, of course not.'

Then what is it you've discovered?'

'Yes. Well... it seems rather obvious now that the operation Potter performed may be repeatable - given that general type of embryo and proper administration of sperm prota- mine.'

Schruille shuddered.

'Have you deduced the course of the operation?' Calapine asked.

'Not precisely, but in outline, yes.'

'Potter could repeat it?' she asked.

'Perhaps even Svengaard.'

'Guard and preserve us,' Calapine muttered. It was a ritual formula whose words seldom caught an Optiman's conscious attention, but she heard herself this time and the word 'preserve' stood out as though outlined in fire. She whirled away.

'Where is Max?' Schruille asked.

The whine in Schruille's voice brought a sneer to Nourse's lips.

'Max is working,' Nourse said. He is busy.'

Schruille looked up at the watching scanners, thinking of all their fellows behind those lensed eyes - the Actionists seeing events as a new demand upon their talents, not realizing what violence might be unleashed here; the Emotionals, fearful and complaining, rendered almost ineffective by guilt feelings; the Cynics, interested by the new game (most of the watchers, Schruille felt, were Cynics); the Hedonists, angered by the current sense of urgent emergency, worried because such matters interfered with their enjoyments; and the Effetes, looking in all this for something new at which to sneer.

Will we now develop a new party? Schruille asked himself. Will we now have the Brutals, all sensitivity immured by the needs of self-preservation? Nourse and Calapine haven't faced this as yet.

Again, he shuddered.

'Max calls,' Calapine said. 'I have him in my transient screen.'

Schruille and Nourse flicked their channel duplicators, looked down at Allgood's swarthy, solid, muscular figure in the transient screen.

'I report,' Allgood said.

Calapine watched the Security chiefs face. He appeared oddly distracted, fearful.

'What of Potter?' Nourse asked.

Allgood blinked.

'Why does he delay his answer?' Schruille asked.

'It's because he worships us,' Calapine said.

'Worship is a product of fear,' Schruille said. 'Perhaps there's something he wishes to show us, a projection or an evidential sub-datum. Is that it. Max?'

Allgood stared out of the screen, looking from one to the other. They'd gotten tied up in that lost-time sense again, the endless word play and disregard for time in the quest for data, data, data - that side effect of endless life, the supra-involve-ment in trivia. This time, he hoped it would go on without end.

'Where is Potter?' Nourse demanded.

Allgood swallowed. 'Potter has... temporarily eluded us.' He knew better than to lie or evade now.

'Eluded?' Schruille asked.

'How?' Nourse asked.

There was... violence,' Allgood said.