And Ben Kamen was ready too. Sleeping, Ben looked very young, younger than his twenty-five years. There was nothing about him to suggest his origin, as an Austrian Jew. One hand still held his fountain pen; the other was folded under his left cheek. His features were small, his skin pale.

Rory looked over what was assembled here: the brooding machine, the boy. This was the Loom, as he and Ben had come to call it, a machine of electromechanics and human flesh which – so they believed, so their theories indicated – could be used to change the warp and weft of the tapestry of time itself. And yet none of it was his, Rory's. Not the Vannevar Bush Analyser which was being loaned to the two of them by MIT; they were students of the Institute of Advanced Studies at Princeton, and they had come here to Cambridge ostensibly to run complex relativistic models with the Analyser. Not the dreaming boy himself – and still less the contents of his head. All that Rory O'Malley owned was the will, to bring these components together, to make it so.

Rory pulled a lock of black hair back from Ben's brow. He wore it too long, Rory thought. Ben didn't stir, and Rory wasn't surprised. The sleeping draught he had poured into Ben's midnight coffee was strong enough to ensure that. Ever since their time together serving in the International Brigade in Spain Rory had always been fond of Ben, poor, deep, intense Ben. But he needed him too, or at least the peculiar abilities locked up in that head of his. Rory saw no great contradiction in this mixture of manipulation and affection. He was intent after all on nothing less than a cleansing of history, a reversal of the greatest crime ever committed. What was a little subterfuge compared to that?

He pulled a scrap of paper from his jacket pocket. It bore a poem of sixteen lines in English, translated roughly into Latin. He scanned it one last time. This was the core of his project, a mandate to history laden with all the meaning and purpose he could cram into it. Now these words would be sent out into the cosmos, crackling along Godel's closed timelike curves like Morse dots and dashes on a telegraph wire – all the way from the future to the past, where some other dreaming head would receive it. All he had to do was to read to Rory, read out the Godel trajectories computed by the Analyser, read the bit of doggerel. That was all, like reading to a child. And everything would change.

Ben stirred, murmuring. Rory wondered where in the many dimensions of space and time his animus wandered now.

Rory began to read. '"Ah child! Bound in time's tapestry, and yet you are born free/Come, let me sing to you of what there is and what will be…'

The boy slept beside the calculating engine.

And then-

Julia Fiveash seduced Ben Kamen. No, she consumed him.

She took him inside three days of her arrival in Princeton from England. He couldn't have stopped her if he'd tried. He wasn't a virgin, with men or women, but after she pushed him to the carpet of his room and wrapped him in her long English limbs he felt as if he had been, before.

The second time they made love it was actually in the study of his mentor, Kurt Godel. And Ben started to fret about her motives.

He lay on Godel's sofa, his jacket pulled over his crotch for modesty. Julia, boldly unclothed, stalked around Godel's room, flicking through the papers on his desk, running her delicate fingertip over the books on the shelves. Many of the books were still in their boxes, for Godel had not been here long; reluctant to leave his beloved Vienna, he had hesitated until the last possible minute, when the Nazis had already started to roll up Europe like a giant carpet.

Julia's golden hair shone in a shaft of dusty sunlight. She was tall, her limbs long and muscular, her belly flat, her breasts small; she walked like an animal, balanced, confident. Her body was the product of a lifetime of English privilege, Ben thought, a life of horse-riding and tennis, her sexuality mapped by one healthy Englishman after another. She had conquered Ben as easily as the English had conquered much of the planet.

He longed for a cigarette, but he knew he dare not light up in Godel's own room.

He plucked up his courage to challenge her. 'What are we doing here, Julia? What do you want?'

She laughed, a throaty sound. She was twenty-eight, three years older than he was; her age showed in her voice. 'That's not a very nice question. What do you think I want?'

'I don't know yet. Something to do with Godel. You used me to get you in here, didn't you? Into this study.'

'Can you blame me for that? Kurt Godel is the world's greatest logician. He's building a new mathematics, so they say. Or dismantling the old. Something like that, isn't it true?'

'You're a historian. You're attached to Princeton University, not this institute of math and physics. Why would you care about Godel?'

'You're ever so suspicious, aren't you? But those suspicions didn't make you fight me off. He's such a funny little man, isn't he? Short and shabby with that high brow and his thick glasses, scuttling like a rabbit in his winter coat.'

'He's been known to take lovers among his students. Despite his unprepossessing looks. I mean, he's still only in his thirties. Back in Vienna-'

'The first time I spotted Godel he was walking with Einstein. Now you can't miss Einstein, can you? Do you know, he was walking in carpet slippers, out in the middle of the street! Is he friendly with Godel, do you know?'

'They met in 1933, I believe. Friends – I don't know. Einstein is the most exotic of the European beasts here in this American zoo, I suppose. But even Einstein had to flee Hitler.'

'Ah, Hitler! I've been in his presence, you know.'

'Whose?'

'Hitler's. I shook his hand. I wouldn't claim to have met him, exactly; I doubt he remembers me at all. I was an exchange student. I wanted to see for myself what the Germans were up to, rather than swallow the usual horrid propaganda. The transformation of that country from economic ruin in just a few years is remarkable. They made us very welcome. Hitler has a very striking presence; he has a way of looking through you. Goebbels, on the other hand, pinched my bum.'

He laughed.

'And now you've all come scuttling here, haven't you? Running from the monster, all the way to America.' She wrinkled her nose. 'Such a poky, dusty room, to be lodging a world-class mind. Godel should have come to Oxford. Einstein too. Better than this. I mean, they have cloisters built of brick! Bertrand Russell says that Princeton is as like Oxford as monkeys could make it.' She laughed prettily.

'Perhaps Einstein and Godel feel safer here than in an England which contains such people as you.'

'You're not very nice to me, are you, all things considered? Anyway Godel would be under no threat in the Reich. He's not even a Jew.' She began plucking books from the shelf, and flicked through their worn pages.

Ben gathered his clothes from where they had been scattered on the floor, and began to pull them on. 'You've had your fun. Maybe it's time you told me what you want from me.'

'Well, there are rumours about you,' she said smoothly. 'You and your professor. Look at these titles. Being And Time by Martin Heidegger. An Experiment With Time by John William Dunne. On the Phenomenology of the Consciousness of Internal Time, Edmund Husserl. You worked with Godel in Vienna, and now that he is here at the IAS you're starting to work with him again, aren't you? But not on the outer reaches of mathematical logic.' She glanced at a pencil note on the flyleaf of the Husserl, scrawled by Godel himself. 'My German is still poor… "The distinction between physical time and internal time-consciousness. Is that right?' As she leafed through the books there was a scent of dust, and stale tobacco – of Vienna. 'Ah. The Time Machine by H.G. Wells. Thought I'd find that here!'