Robert shifted uneasily on his chair. Helen hadn't sworn him to secrecy, but he'd agreed with her view: it was better to wait, to spread the knowledge that would ground an understanding of what had happened, before revealing any details of the contact between branches.

But this man's wife was dying, needlessly. And Robert was tired of keeping secrets. Some wars required it, but others were better won with honesty.

He said, "I know you hate H.G. Wells. But what if he was right, about one little thing?"

Robert told him everything, glossing over the technicalities but leaving out nothing substantial.

Hamilton listened without interrupting, gripped by a kind of unwilling fascination. His expression shifted from hostile to incredulous, but there were also hints of begrudging amazement, as if he could at least appreciate some of the beauty and complexity of the picture Robert was painting.

But when Robert had finished, Hamilton said merely, "You're a grand liar, Stoney. But what else should I expect, from the King of Lies?"

Robert was in a somber mood on the drive back to Cambridge. The encounter with Hamilton had depressed him, and the question of who'd swayed the nation in the debate seemed remote and abstract in comparison.

Helen had taken a house in the suburbs, rather than inviting scandal by cohabiting with him, though her frequent visits to his rooms seemed to have had almost the same effect. Robert walked her to the door.

"I think it went well, don't you?" she said.

"I suppose so."

"I'm leaving tonight," she added casually. "This is goodbye."

"What?" Robert was staggered. "Everything's still up in the air! I still need you!"

She shook her head. "You have all the tools you need, all the clues. And plenty of local allies.

There's nothing truly urgent I could tell you, now, that you couldn't find out just as quickly on your own."

Robert pleaded with her, but her mind was made up. The driver beeped the horn; Robert gestured to him impatiently.

"You know, my breath's frosting visibly," he said, "and you're producing nothing. You really ought to be more careful."

She laughed. "It's a bit late to worry about that."

"Where will you go? Back home? Or off to twist another branch?"

"Another branch. But there's something I'm planning to do on the way."

"What's that?"

"Do you remember once, you wrote about an Oracle? A machine that could solve the haltingproblem?"

"Of course." Given a device that could tell you in advance whether a given computer program would halt, or go on running forever, you'd be able to prove or disprove any theorem whatsoever about the integers: the Goldbach conjecture, Fermat's Last Theorem, anything. You'd simply show this "Oracle" a program that would loop through all the integers, testing every possible set of values and only halting if it came to a set that violated the conjecture. You'd never need to run the program itself; the Oracle's verdict on whether or not it halted would be enough.

Such a device might or might not be possible, but Robert had proved more than twenty years before that no ordinary computer, however ingeniously programmed, would suffice. If program H could always tell you in a finite time whether or not program X would halt, you could tack on a small addition to H to create program Z, which perversely and deliberately went into an infinite loop whenever it examined a program that halted. If Z examined itself, it would either halt eventually, or run forever. But either possibility contradicted the alleged powers of program H: if Z actually ran forever, it would be because H had claimed that it wouldn't, and vice versa. Program H could not exist.

"Time travel," Helen said, "gives me a chance to become an Oracle. There's a way to exploit the inability to change your own past, a way to squeeze an infinite number of time-like paths-none of them closed, but some of them arbitrarily near to it-into a finite physical system. Once you do that, you can solve the halting problem."

"How?" Robert's mind was racing. "And once you've done that what about higher cardinalities? An Oracle for Oracles, able to test conjectures about the real numbers?"

Helen smiled enigmatically. "The first problem should only take you forty or fifty years to solve. As for the rest," she pulled away from him, moving into the darkness of the hallway, "what makes you think I know the answer myself?" She blew him a kiss, then vanished from sight.

Robert took a step toward her, but the hallway was empty.

He walked back to the car, sad and exalted, his heart pounding.

The driver asked wearily, "Where to now, sir?"

Robert said, "Further up, and further in."

4.

The night after the funeral, Jack paced the house until three a.m. When would it be bearable? When?

She'd shown more strength and courage, dying, than he felt within himself right now. But she'd share it with him, in the weeks to come. She'd share it with them all.

In bed, in the darkness, he tried to sense her presence around him. But it was forced, it was premature. It was one thing to have faith that she was watching over him, but quite another to expect to be spared every trace of grief, every trace of pain.

He waited for sleep. He needed to get some rest before dawn, or how would he face her children in the morning?

Gradually, he became aware of someone standing in the darkness at the foot of the bed. As he examined and reexamined the shadows, he formed a clear image of the apparition's face.

It was his own. Younger, happier, surer of himself.

Jack sat up. "What do you want?"

"I want you to come with me." The figure approached; Jack recoiled, and it halted.

"Come with you, where?" Jack demanded.

"To a place where she's waiting."

Jack shook his head. "No. I don't believe you. She said she'd come for me herself, when it was time. She said she'd guide me."

"She didn't understand, then," the apparition insisted gently. "She didn't know I could fetch you myself. Do you think I'd send her in my place? Do you think I'd shirk the task?"

Jack searched the smiling, supplicatory face. "Who are you?" His own soul, in Heaven, remade?

Was this a gift G.o.d offered everyone? To meet, before death, the very thing you would become-if youso chose? So that even this would be an act of free will?

The apparition said, "Stoney persuaded me to let his friend treat Joyce. We lived on, together. More than a century has pa.s.sed. And now we want you to join us."

Jack choked with horror. "No! This is a trick! You're the Devil!"

The thing replied mildly, "There is no Devil. And no G.o.d, either. Just people. But I promise you: people with the powers of G.o.ds are kinder than any G.o.d we ever imagined."

Jack covered his face. "Leave me be." He whispered fervent prayers, and waited. It was a test, a moment of vulnerability, but G.o.d wouldn't leave him naked like this, face-to-face with the Enemy, for longer than he could endure.

He uncovered his face. The thing was still with him.

It said, "Do you remember, when your faith came to you? The sense of a shield around you melting away, like armor you'd worn to keep G.o.d at bay?"

"Yes." Jack acknowledged the truth defiantly; he wasn't frightened that this abomination could see into his past, into his heart.

"That took strength: to admit that you needed G.o.d. But it takes the same kind of strength, again, to understand that some needs can never be met. I can't promise you Heaven. We have no disease, we have no war, we have no poverty. But we have to find our own love, our own goodness. There is no final word of comfort. We only have each other."

Jack didn't reply; this blasphemous fantasy wasn't even worth challenging. He said, "I know you're lying. Do you really imagine that I'd leave the boys alone here?"

"They'd go back to America, back to their father. How many years do you think you'd have with them, if you stay? They've already lost their mother. It would be easier for them now, a single clean break."

Jack shouted angrily, "Get out of my house!"

The thing came closer, and sat on the bed. It put a hand on his shoulder. Jack sobbed, "Help me!"

But he didn't know whose aid he was invoking any more.

"Do you remember the scene in The Seat of Oak? When the Harpy traps everyone in her cave underground, and tries to convince them that there is no Nescia? Only this drab underworld is real, she tells them. Everything else they think they've seen was just make believe." Jack's own young face smiled nostalgically. "And we had dear old Shrugweight reply: he didn't think much of this so-called 'real world'

of hers. And even if she was right, since four little children could make up a better world, he'd rather go on pretending that their imaginary one was real.

"But we had it all upside down! The real world is richer, and stranger, and more beautiful than anything ever imagined. Milton, Dante, John the Divine are the ones who trapped you in a drab, gray underworld. That's where you are now. But if you give me your hand, I can pull you out."

Jack's chest was bursting. He couldn't lose his faith. He'd kept it through worse than this. He'd kept it through every torture and indignity G.o.d had inflicted on his wife's frail body. No one could take it from him now. He crooned to himself, "In my time of trouble, He will find me."

The cool hand tightened its grip on his shoulder. "You can be with her, now. Just say the word, and you will become a part of me. I will take you inside me, and you will see through my eyes, and we will travel back to the world where she still lives."

Jack wept openly. "Leave me in peace! Just leave me to mourn her!"

The thing nodded sadly. "If that's what you want."

"I do! Go!"

"When I'm sure."

Suddenly, Jack thought back to the long rant Stoney had delivered in the studio. Every choice went every way, Stoney had claimed. No decision could ever be final.

"Now I know you're lying!" he shouted triumphantly. "If you believed everything Stoney told you, how could my choice ever mean a thing? I would always say yes to you, and I would always say no! It would all be the same!"

The apparition replied solemnly, "While I'm here with you, touching you, you can't be divided. Yourchoice will count."

Jack wiped his eyes, and gazed into its face. It seemed to believe every word it was speaking. What if this truly was his metaphysical twin, speaking as honestly as he could, and not merely the Devil in a mask? Perhaps there was a grain of truth in Stoney's awful vision; perhaps this was another version of himself, a living person who honestly believed that the two of them shared a history.

Then it was a visitor sent by G.o.d, to humble him. To teach him compa.s.sion toward Stoney. To show Jack that he too, with a little less faith, and a little more pride, might have been d.a.m.ned forever.

Jack stretched out a hand and touched the face of this poor lost soul. There, but for the grace of G.o.d, go I.

He said, "I've made my choice. Now leave me."

Author's note: Where the lives of the fictional characters of this story parallel those of real historical figures, I've drawn on biographies by Andrew Hodges and A.N. Wilson. The self-dual formulation of general relativity was discovered by Abhay Ashtekar in 1986, and has since led to ground-breaking developments in quantum gravity, but the implications drawn from it here are fanciful.

To Cuddle Amy

NANCY KRESS.

Nancy Kress is one of the major SF writers of the last two decades, well-known for her complex medical SF stories and for her biological and evolutionary extrapolations in such cla.s.sics as Beggars in Spain (1993), Beggars and Choosers (1994), and Beggars Ride (1996). In recent years, she has written two science thrillers, Oaths and Miracles (1995) and Stinger (1998), the SF novel Maximum Light (1998), and last year published Probability Moon (2000), the first book in a trilogy of hard SF novels set against the background of a war between humanity and an alien race. In 1998 she married SF writer Charles Sheffield. Her stories are rich in texture and in the details of the inner life of character and have been collected in Trinity and Other Stories (1985), The Aliens of Earth (1993), and Beakers Dozen (1998). She teaches regularly at summer writing workshops such as Clarion, and during the year at the Bethesda Writing Center in Bethesda, Maryland. She is the "Fiction" columnist for Writers Digest.

"To Cuddle Amy" is a tiny SF horror story with a sit-com tone. It appeared in Asimov's. It is an interesting contrast to Michael Flynn's story, "Built Upon the Sands of Time." There were a number of stories published last year about the anxieties of parents and children in the coming era of genetic engineering that is creeping up on us, but none better than this one.

Campbell entered the living room to find his wife in tears. "Allison! What's wrong?"

She sprang up from the sofa and raged at him. "What do you think is wrong, Paul? What's ever wrong? Amy! Only this time she's gone too far.

"This time, she...she... the police just left...." She broke down into sobs.

Campbell had had a lot of experience dealing with his wife. They'd been married almost forty years.

Pushing down his own alarm, he took Allison in his arms and sat on the sofa, cradling her as if she were a child. Which, in some ways, she still was. Allison had always been high strung, finely tuned. Sensitive. He was the strong one. "Tell me, sweetie. Tell me what happened."

"I...she..."

"The police. You said the police just left. What did Amy do now?"

"Van...vandalism. She and those awful friends of hers... the Hitchens boy, that s.l.u.t Kristy Arnold...

they...""They what? Come on, honey, you'll feel better if you tell me."

"They were throwing rocks at cars from the overpa.s.s! Throwing rocks!"

Campbell considered. It could be far worse. Still... something didn't add up here. "Allison-why did the cops leave? Are they going to arrest Amy?"

"No. They said they"-more sobbing-"couldn't be sure it was her. Not enough evidence. But they suspected it was, and wanted us to know... oh, Paul, I don't think I can take much more!"

"I know, honey. I know. Shhh, don't cry."

"She just throws away everything we do for her!"