'So why did he come back?'

The Doctor shrugged. 'I think maybe he didn't want to go through with it until he was absolutely sure he had to. Until he knew there was no other way. He needed to talk to Holiday Sabbath, he wanted to know whether Naryshkin had another solution. He was scared, Fitz,' The Doctor finally lifted his hand from Fitz's shoulder. 'We're all scared,' he admitted quietly.

'He still killed Galloway,' Fitz said. 'Didn't you?'

George nodded. 'Yes, I did. I didn't mean to. He wanted to discuss how to approach the palaeontology, that's what he said. So I went to his tent.' The emotion of the memory was etched on George's translucent face. 'Then he attacked me went for me with a knife.' He stepped towards Fitz, hand out, pleading. 'I had to stop him, to defend myself. I grabbed the first thing that came to hand, and I hit him with it. I thought I might drive him off, or even knock him out. But when I saw what happened, what I was holding... 'His voice dropped away to nothing and George's head bowed.

'A tent peg,' Fitz said slowly. 'You hit him with a tent peg.' He shook his head. 'Why didn't you say that's what happened?'

'Galloway thought I was going to expose him, ruin him. As if I could. What good would it do to tell everyone the truth after he was dead. And who'd believe me anyway?'

'So you let me take the blame?'

'No... That just happened. I thought maybe it would be seen as an accident.'

'Yeah, right.' Fitz blew out a long misty breath. 'But you couldn't say "oh yes, I saw Fitz, he was asleep in his tent," could you?'

'I'm sorry, Fitz. But I didn't know. What if you hadn't been? What if you were with Caversham or Price or someone? Then you'd all know I was lying, all know that I'd I'd killed him.' He turned away. 'I didn't think, not for a second, that anyone would suspect you, Fitz. That was stupid, and I'm sorry. I suppose I just thought that everyone else shared my opinion about you.'

Fitz blinked. 'What opinion? What do you mean?'

'That you're a decent, honest person,' George said. 'That you'd do anything to help if you thought it was for the best, and never hurt anyone. That you'd go to Siberia on a whim just because someone you respected asked you. That you're dependable and brave and the best friend a man could have.'

As he spoke, George turned slowly to face the Doctor. 'I'm ready,' he said. 'I've made my decision.'

Fitz was still shaking. Anji could see the light glistening on a single tear that escaped from his eye. Watched as it froze on his cheek. 'George...' His voice was a husky rasp. He choked, swallowed. 'George, I'm sorry. I'm sorry about everything.'

Anji wiped her own eyes.

'You can't do it, George,' Fitz blurted. 'There has to be some other way.' He looked at the Doctor.

Anji followed Fitz's gaze. They were all looking at the Doctor now.

But his face was impa.s.sive, as cold and empty as ice.

Time Zero

There was a soldier on guard at the door. Trix and Sabbath were sitting on opposite sides of one of the tables in the cafeteria area of the Great Hall. Around them, ghostly shadows of past events played themselves out.

People ran, died, made coffee and ate and laughed. It was like a haze if Trix focused on them, she could make out the individuals. She could see the area where the cafeteria section had been set up either with or without the modern walls. Even the table she was sitting at seemed somehow less solid than it had a few minutes earlier.

She smiled at the soldier in the doorway, trying not to let herself be distracted as a heavy wooden door that wasn't there was battered down by an enormous creature that seemed half*lizard, half*dinosaur. 'Is he right, do you think?' she said.

Sabbath was staring down at the table. His huge hands rested on the surface and he seemed to be inspecting the lines and creases on them. 'The Doctor?' he asked without looking up.

'No,' she said patiently, 'the King of Tibet.'

He did look up now. A slight smile on his face. 'Who you have met, no doubt?'

'We're old friends. Of course the Doctor. Is the world going to end, or the universe split up or get smashed together or whatever catastrophe he was going on about?'

Sabbath's smile faded. 'He may be right,' he admitted. 'He may actually be right about it. It's possible that I have not been told the entire truth. For whatever reason.'

'That'll be it,' Trix said in an understanding tone. 'Someone else made a mistake. Couldn't be, I suppose, that you're just plain wrong for once, could it?' She raised her eyebrows. 'Thought not.'

'You are a very annoying woman, Miss MacMillan. If that really is your name.'

She smiled and threw her head back so that her hair rearranged itself in a neat bob. 'It might be,' she said. 'That's sort of, what's the word? Indeterminate.' She considered for a moment, sucking in her cheeks and pouting her lips. 'If that is actually a word at all.'

'If the Doctor is correct,' Sabbath said slowly, as if to himself, 'then what he is doing is not without hazard.'

'You mean it's dangerous.'

'In the extreme.'

'Like either the world ends, or he blows us all up saving it? That sort of extreme?'

Sabbath's eyes narrowed, seeming to recede into his round face. 'Rather worse than that, I'm afraid.'

'Just so we know.' She stood up and stretched. 'Fancy a coffee?'

'The different universes are already overlapping.'

'I'd noticed,' she called back as she went over to the kitchen area, 'If the Doctor is too late, or if the energy is not completely dissipated, then the whole of reality might be thrown into confusion.'

'And we'd notice, would we?' Trix called back.

But Sabbath seemed not to hear. 'Different versions of history play out in parallel. No longer separated by the thin membrane of reality. A universe where different sequences of different events exist and coexist side by side, overlapping, intersecting, merging.'

Trix reappeared with a mug of water.

'The Doctor was right about one thing,' Sabbath admitted. 'He and I travel back and forth within the same reality, the same Quantum Universe.'

'I seem to recall,' Trix said sipping from the mug, 'that he used that as a rather emphatic indication that you were in the wrong. Or did I mishear that bit?'

Sabbath stood up suddenly, his chair skidding backwards and toppling over as it struck the edge of a flagstone. His face was reddening as he spoke. 'Yes, I was wrong! Happy now, Miss MacMillan?'

Trix seemed unperturbed. 'Well, apart from the overlapping, intersecting, merging reality bit.' She sat down. 'What were you proposing to do about that? If it happens? And if we can even tell that it's happened?'

'There was always a chance I might not succeed here,' Sabbath said. He picked up the chair and sat down again.

'No?!' Trix sounded scandalised at the thought.

He glared at her: 'It is as well to be prepared.'

'My great grandfather used to say that. He was Baden*Powell, you know.'

Sabbath stared at her. 'Really?'

'No, not really,' she said, 'He was the Tsar of all the Russias, remember?'

'Was he?'

Her eyes were wide and innocent. 'Scout's honour. So what was your back*up plan, not that it matters if we're all going to die horribly anyway.' She waved a hand to shoo off someone who had just walked through her. 'This is all rather disconcerting to an inexperienced la.s.s from the country like me, you know.'

'I have to get away from this world,' Sabbath said quietly.

'Urgent appointment, eh?'

'A race against infinity.' He was smiling again, as if he had made a joke he knew she would not appreciate.

'So how will you get to this world? How do you travel in time, a.s.suming for the moment that I accept time travel is possible at all?'

'In the same way as the Doctor would, only with rather more style. I just need to get back to my ship.' As he spoke he drew something from his pocket. It was a boat, a small plastic model of a streamlined speed boat. He turned it over in his hand, examining the detail.

'Is that your ship?'

Sabbath shook his head. 'Well, it belongs to me, but it isn't a model of the Jonah Jonah. This is just something I picked up on my travels. It gave me the idea for my next port of call, shall we say?' He smiled, evidently amused by his own joke.

Trix clicked her tongue, her eyes fixed on the model Sabbath was holding. 'Such a shame about the guard on the door.' She leaned across the table and stared appealingly at Sabbath. 'Tell me about the Doctor,' she said.

'Why?' He looked up abruptly, returning tile model to his pocket.

'Because I'm interested.' She leaned back and folded her arms. 'And because, if you tell me about the Doctor, I'll tell you about the secret pa.s.sage he used earlier to escape from this very room. How's that for a deal?'

The grenade was warm in Fitz's hand, even through the glove. Time seemed to slow as he held it out in front of him; as he reached outt his other hand and grasped the metal pin; as he pulled. As it came free.

History was a blur. Curtis was running now, breaking through the years. He saw the blood and terror of the Russian Revolution going on around him, was tempted to stop, take the time to watch. Perhaps on the way back, when he was free of the numbing, icy blackness that clouded his mind and fogged his senses.

The creature before them paused, its head slightly to one side as if puzzled, watching. George was yelling at Fitz, mouth working, but no sound. No sound at all. Underwater pressure in his ears as Fitz lobbed the grenade.

But not at the creature.

At the wall of ice where the tiny flames flickered, where the impossible fires were frozen.

Trix was standing close beside Sabbath as he concentrated, her fingers edging towards his jacket pocket. He was staring at the fireplace where Trix had pointed. He saw the shadowy image of Fitz grabbing the tapestry as the creature leaped across the room. Saw the doorway swing open.

The soldier at the main door was worried, could see something was wrong, was coming over.

The grenade twisted in the air; then skidded and bounced until it rested at the foot of the huge gla.s.sy wall.

The image of the doorway by the fireplace solidified. All the images were becoming more solid, more real, as reality itself was ripped apart.

The soldier was running, shouting, could see Fitz and the monster and the secret doorway.

Sabbath was running too, diving for the opening even as it shimmered in and out of possible existence.

The first explosion was almost a disappointment. An orange flare reflecting off the ice and percussing round the chamber. A billow of dark smoke. The creatures flinching, backing away. As the smoke cleared, Fitz could see that the whole wall of ice was glowing the flames inside erupting outwards, racing towards him as they broke free of the ice and threw its shattered remains across the cavern.

Decision taken, choice made, George Williamson stepped into the ice. For a moment his shimmering translucent silhouette seemed to merge and overlap and intersect with the shadowy figure barely visible within the ice.

For a moment he was able to stare back and see the Doctor and Anji and Fitz looking at him. He saw the sadness and the hope and the friendship in their eyes.

He started running, back towards 1894. Towards the beginning and the end of things.

Fitz pushed George, with all his might, hoped he would reach the shelter of a huge chunk of ice that had fallen from the ceiling.

Gasping for breath, George stepped out of the ice. His hands, he noticed, seemed more real, more solid now. But he had no time to wonder about this. In front of him, Fitz was shoving a figure across the cavern towards George.

And the figure was himself.

Fitz had turned away, diving backwards as George's own past self fell towards the ice wall, towards the light that shone out from the glacial wall cracking open from the grenade's blast which still echoed round the cave.

George the George that Fitz had pushed out of danger fell to the floor, scrambled up, was about to dive for the scant protection offered by the overhanging roof of ice.

Then he stopped. Stared. Saw himself staring back.

A faint image, an imprint in the air dived for cover, was caught in the light and blinked in surprise and disbelief.

But the solid, real George stood and stared and did not move.

The ice was crashing down, the roof collapsing, another explosion building and rumbling deep within the fiery ice.

George nodded, smiling at the confused version of himself that was now trapped and about to die. The one who had never entered the ice or been frozen in time. And he felt himself slipping away, fading gradually to nothing. Like a ghost.