Strangely, she didn't look out of place in uniform. He announced his presence.

She turned, wearily. 'Hi, George.' Her attention returned to the photographs. Her accent was still utterly impossible to place, containing elements of South African and American as well as English.

'Captain Forrester, it's getting late.'

'Yes, I know, but there's still so much to do.'

'Permission to speak freely, Captain?'

'Granted.' She looked up from her work.

'You were right this afternoon, Captain. The admiral wasn't treating you as your rank deserves. If I have done so, then I offer my apologies. I like you, ma'am, and wouldn't want to upset you.' He had spent most of the day planning this speech.

It seemed to work. Roz smiled at him, and there was genuine warmth there. 'Thank you, Lieutenant. Apology accepted, but it's my fault. What I did this morning was unprofessional. It doesn't matter whether I was provoked or not.'

'Ma'am, I -'

'End of story, George. Look, do you mind walking me home? The tube closes at six and there's no way Kendrick will spare a staff car. I'm not sure I'd be able to find Paddington by myself.' George's heart raced, and he eagerly accepted. She stood, folding over a couple of sheets of paper, and placing the photographs in the safe. He reached across for Forrester's coat and gas mask.

'Captain, may I ask you a question?'

'As long as you don't expect an answer. Joke.'

'Ah, yes. I wanted to ask about that tribe you mentioned before. The Servobots.'

Roz broke eye contact and she found another piece of paper to turn over. 'Yeah, what about them?'

'Well, I've read a bit about the South African tribes, and I've not heard of them.'

Chris made his way carefully across the fields. The airstrip was meant to be a mile to the north of here, but very little was known about it. There were certainly German patrols, with dogs and torches, but they made a lot of noise and were easy enough to avoid. Visibility was poor now; fog had drifted in off the sea. It would be a lot easier if he'd been allowed to bring his IR goggles, but the Doctor had made it clear why he couldn't. If he was captured, or if he just dropped them, then the Germans might just work out how to duplicate the technology. The consequences could be horrendous: foot patrols would find it easier to pick up people, U-boats would be able to detect convoys, aerial reconnaissance would enter a whole new era. It wouldn't take the n.a.z.is long to work out that they could link up IR sensors to an antiaircraft battery or to put it in one of their planes. All of a sudden, it would become very easy to spot Allied aircraft, and all because he dropped his goggles.

Chris needed to rest. He'd hardly slept for twenty-four hours. He had to find somewhere safe to settle for the night.

It was just possible to make out a building a couple of hundred yards away, black against the royal-blue sky. It might fit the bill. A car darted past him as he made his way forward. The building was a large brick barn. Fifty yards away was a collection of farm buildings: a farmhouse, a stable, some sort of chicken shed. All were blacked out. There was the sound of a dog barking in the middle distance, but it wasn't getting any closer. The animal was probably chained up.

Chris made his way round the sides of the barn until he found the door. It was unlocked. He prised open the door and stepped inside. It was pitch black. After a few moments fumbling around, Chris established that there was nothing in here but a few bales of hay. The door he had come through was the only way in. He rearranged a couple of the bales, setting up some cover.

He was just settling down when the door burst open, and a torch was shone in his face. He raised his hands to shield his eyes. Behind the light, he could make out one, no, two figures. He reached for his revolver, and was greeted by the sound of two guns being c.o.c.ked. He decided against it.

The soldier on the door saluted Forrester and Reed as they left the War Office. Reed led the way across Whitehall, all the time nervously looking back at Roz, checking that she was still with him, asking if she was all right. His overwhelming urge to appear concerned and his dogged desire to be liked reminded her of Chris.

Even in wartime, the London streets were normally busy with buses, cars and horse-carts during the day, but now they were almost deserted. Barrage balloons jostled in the sky. It was still only twilight, but it seemed darker, as no street lighting was permitted. The Doctor had claimed that when the restrictions on car headlamps and street lighting had first been introduced, the number of accidents had increased so dramatically that more people died on the roads than in air-raids. The blackout had been relaxed a little since then.

This was the first time that Forrester had walked any distance through London. As they picked their way past ruined terraces and cratered roads, she suddenly realized where she was. They were walking through a wide public s.p.a.ce, surrounded by huge old buildings. In the middle of the plaza was a huge pillar, standing alone. As an Adjudicator, she had walked these streets in the thirtieth century, and the layout of the place was hardly different. In her day, the Underdwellers called this place Trafflegarr Square, and they were walking towards Sintjaimsys. Those in the Overtowns didn't really distinguish. To them, all this area was s.p.a.ceport Five Undertown.

'This hasn't changed in a thousand years.'

'No. And it probably won't for another thousand,' Reed answered. Roz was about to explain, but thought better of it.

As George said, the city was an old one. There was no reason why it should have changed that much. Individual houses and office blocks came and went, but the basic layout of the streets themselves stayed the same. It was amazing, though, that many of the buildings that were already centuries old at this time would still be standing in a millennium.

'Whereabouts do you live?' Roz asked, wondering whether she'd recognize Reed's house.

'I've got a flat in Mayfair, not far from here. I'm on this side of Hyde Park, you're on the other.'

Again, it was a name Roz recognized from her time.

From Reed's tone of voice, it was clear that Mayfair in this time was somewhat more prestigious than in hers.

There was someone blowing a whistle in the next street.

Reed grabbed her by the arm. 'It's an air-raid. We have to get inside.'

Will your flat do?'

Reed nodded grimly. 'It's a bas.e.m.e.nt flat. We should have enough time, usually we get about ten minutes'

warning. We'll have to hurry.'

Reed broke into a run, although Roz found it easy to keep up. He was already fishing in his pocket for his keys.

They were running along a row of elegant terraces straight out of a Sherlock Holmes simcord. When Roz looked up, the sky had become a cathedral of light. Solid white beams criss-crossed the night sky, creating a rippling net in the heavens.

A thousand years from now, people would pay good money to see a light-show like this. Hardly anyone saw this spectacle, though. Every night, millions of Londoners sat in their Anderson shelters, or in the Underground railway stations. Above ground, searchlight crews probed the sky for German bombers. If one beam intercepted a plane, half a dozen more would instantly be brought to bear. Bathed in light, the German planes would be easy targets for the antiaircraft batteries.

Right on cue, a mile or so behind them, there was a burst of artillery fire. It wouldn't hit a plane. Over the last three months, half a million sh.e.l.ls had been fired, but, on average, only one bomber a night was brought down. The British wouldn't admit it, but the guns were there to rea.s.sure their civilians, not as a practical way of defending them.

George ushered her down a flight of stone steps to his dark blue front door, warning her that there wasn't a railing any more. After a moment struggling with the lock, they were inside.

George's hallway smelt faintly of boiled vegetables. Roz was occupied with this thought while he took her coat, and hung it with his own behind the front door. It was dark, too.

The blackout material was in place and the bulb had been removed to save electricity. George struck a match, lighting a candle. He handed it to Forrester, who examined it. Primitive technology, but effective enough. Reed had a candle of his own, and led her through into his front room. The front room consisted of a sofa, a threadbare rug and an unlit coal fire. In the corner, a big wireless sat on top of a bookcase stuffed with old hardback books. The place was kept spotlessly clean, but because the windows had been painted over with blackout paint, it was claustrophobic. Reed a.s.sured her that they ought to be safe in this room. He excused himself, taking his candle with him.

Roz placed her candle in a metal holder, and began exploring the room. Bernice would love this, she thought, it was just like exploring an excavated Egyptian burial chamber. The candlelight danced off the wall, casting pools of shadow. There was a portrait above the mantelpiece. The subject, an elderly man, bore a strong resemblance to George, but he was bearded and wore a military uniform that Roz knew came from a much earlier time than this. Edging forward, Roz b.u.mped into a small coffee table, knocking the telephone off the hook. She carefully replaced the handset and continued her search. She examined the bookcase. A few scientific textbooks, a couple of spy novels. The The Language and Customs of South Africa Language and Customs of South Africa. She pulled the picture book down, and sat on the settee. The book fell open at a full-page photograph of 'a Xosa maiden'. The image was murky, printed on poor-quality paper. The girl was about fourteen or fifteen, and was Zulu, not Xhosa, as a cursory glance at the dress confirmed. Her skin was relatively light and her nose was not as flat as a typical African. Despite that, the grinning face of this 'Xosa maiden' bore an uncanny resemblance to Forrester's own graduation photograph. The girl in the picture was prettier. Roz read the caption - 'The costume consists mainly of a blanket, beads, wire bracelets and bands round the ankles. At home the blanket is usually dispensed with.' Her b.r.e.a.s.t.s were indeed covered, presumably so as not to offend the sensibility of the English reader.

'Oh, you've found it. I was going to show you.' George had come back with a tray of tea and toast. Roz held up the photograph.

'It seems to have fallen open at this page,' she said sardonically.

Reed blushed, but was unapologetic. 'I got this book for my tenth birthday. You know, for years I couldn't work out what she wore instead of the blanket. Is that how you dress at home?'

Only in your dreams, soldier-boy, Roz thought, but she replied, 'It would certainly turn a few heads in Paddington.'

'I meant at home in Africa,' Reed explained patiently.

'I wore the traditional dress once, at a costume party.'

'You take your ikofu ikofu black because of the black because of the ukuzila ukuzila.' He handed her a mug of thick, black coffee.

'I take it black, because I like the taste, not because of any tribal taboo,' she snapped. At least I think that's the At least I think that's the reason reason. She sipped her hot drink. Reed had lit her a cigarette, which she gratefully accepted.

'I p.r.o.nounced the words right, then, Captain Forrester?

I've been swotting up ever since I found out that you're a Xhosa.'

'You p.r.o.nounced them right, George.' She leant a little closer. 'And call me Roz.'

Outside, the bombs were beginning to drop.

6 Kill All the b.u.t.terflies

On his nineteenth move, the Doctor, playing Black, placed his knight on C5, threatening Steinmann's bishop. The German had predicted this and all he needed to do was...

'I know about Emil Hartung, of course,' the Doctor said quietly. Steinmann looked up at him. On first impression, this Doctor resembled nothing more than a smelly old tramp. The trick was to look into his eyes, gaze beyond the shabby exterior into his labyrinthine, brilliant mind. There you would find true genius, allied with the cunning of a wild animal. The Doctor was an opponent to be reckoned with, in life as well as in chess. Even a bully like Wolff had seen that. This Doctor was proving a fascinating diversion from the business of war, and was the only chess player for over a decade who had come anywhere near to beating him. Steinmann turned his attention back to the board.

'And I know exactly what Hartung is building. Please send him my regards,' the Doctor finished. The words hung in the air for the moment, then the little man said cheerfully, 'There are two kinds of chess-players.' Steinmann looked up again, as the Doctor continued. 'Those who give up when they lose their Queen and those who carry on playing.'

Steinmann moved his bishop out of harm's way. 'An interesting theory, if a little simplistic. Which camp do you belong in, Herr Doktor?'

'Oh, I never lose my Queen. It was just an observation.'

The Doctor pressed his knight forward, capturing the white queen. Steinmann could hardly believe his eyes, and turned his full attention back to the game. 'Which camp are you in?'

the Doctor asked sweetly, as he removed the white piece from the board.

Steinmann knocked his king over. The Doctor grinned.

'Doktor, I congratulate you. You have mastered chess,'

Steinmann offered.

'No,' said the Doctor, 'it isn't possible to. There's always someone better, somewhere.'

A fascinating philosophical point. There are more potential moves in the game of chess than there are atoms in the galaxy, did you know that? The number of moves is finite, though. One day, the solution will be found to every possible chess game. Chess is just a more complicated version of noughts and crosses, or draughts, and a good enough mathematician should be able to work it out.'

The Doctor pursed his lips. 'That's not true. You're right that there are strict rules and only a finite number of moves, but there is a random element to the game: the players themselves. You could never work out your opponent's thoughts, or know his memories. You couldn't predict when he'll cough or when he's bluffing.' Listening to the Doctor's answer, Steinmann found it possible to believe that the little man had tried to square the circle - he talked as if he'd played every possible game, and tried to win them all. Tried and failed. He had won this particular contest, though.

'So you have proved,' Steinmann muttered, sipping at his wine. 'You are right, of course. There is always another set of variables to take into account. It's like that British slogan, "Careless Talk Costs Lives": a London housewife gossiping on the bus might reveal some sensitive information, a spy could overhear and we could use it to win the war. Even with obsessive secrecy, information slips out.'

'There's nothing you can do about it,' said the Doctor gloomily, 'it's the nature of the universe. Congratulations.

You've discovered the b.u.t.terfly Effect eleven years early.

Everything is interrelated: a b.u.t.terfly flapping its wings in Granville might lead to a hurricane sweeping across Berlin.

You can never predict all the consequences of an action. You can never control everything. We all have to muddle along as best we can.'

There is another way, thought Steinmann, we could kill all the b.u.t.terflies. Or make them flap their wings when we order them to. Visions of a party rally swam before his eyes, twenty thousand arms surging skywards in salute. Control the universe, never allow yourself to be controlled by it.

'Would you like another game?' the German offered. The Doctor was already setting up the pieces.

Reed's chest rose and fell steadily beneath Forrester's head, hypnotizing her. He cradled her in his arms, one hand resting in the small of her back, the other on her thigh. There was an intoxicating scent in the air, a blend of cigar smoke, brandy and aftershave. She hadn't felt so relaxed since -

'G.o.ddess!' She bolted upright. George Reed's eyes snapped open, catching her before she fell off the sofa. He looked as surprised as she felt. She stood uncertainly.

'There's nothing wrong. We're at my flat, remember?'

It all came flooding back. They'd talked, smoked and got a bit drunk. Then she'd fallen asleep. That's all. Situation under control.

'Yeah, sure. Sorry.' It was still pitch black in here, thanks to the blackout paint. It was chilly, too. England was so cold in this century. If she didn't know better, then she'd have suspected that this was because the British hadn't discovered fire yet. It was impossible to judge the time of day in here, but she could hear birdsong outside. Roz checked her wrist.w.a.tch.

'It's twenty past eight!'