'Wait a minute,' Nesbitt said. 'You're saying that it isn't the ice that's slowing the light down, freezing it so it seems not to move. It's some property of the light itself, is that right?'

The Doctor had picked up the mug. He looked down into the water, blowing on it to cool it down. 'That's exactly right,' he said. And with that he raised the mug and drank the water down in one. 'That's better,' he said as he replaced the mug on the table. 'Nothing like a warming drink on a cold day.'

'Was that safe?' Lansing asked, stepping away from the Doctor.

'I sincerely hope so. You were right in one respect, you know,' he went on. 'There is an infinite number of o-regions, each developing Iike a mini*universe in its own way. And since you could, in theory though I wouldn't recommend that you try work out every possible collision point and potential change in our own universe to date, that means that there's only a finite finite number of possible histories. Huge, but finite.' number of possible histories. Huge, but finite.'

'And what does that mean?' Nesbitt said.

'It means that every possible version of history that you can imagine will occur.' The Doctor grinned. 'In fact, given the rather strange way that maths with infinity works, it means that every possible version of history will actually occur an infinite infinite number of times.' number of times.'

'Er,' Nesbitt hesitated, 'is this strictly relevant?'

The Doctor shook his head. He was still smiling, but his smile faded as he spoke. 'Not strictly, no. But I'm trying to gain your confidence and respect, remember. Trying to convince you that I know what I'm talking about and that you should act. It's not strictly relevant, more sort of tangential. And fascinating. And frightening too, don't you think? Consider how fragile and thin our own reality must be.'

'So what's the tangential relevance?'

'I won't bore you with the details,' the Doctor said. 'But basically, what it boils down to, is that George Williamson was not frozen in the ice for a century. In fact, George Williamson is not at all what he appears to be.'

7: Confrontation

It was as if the walls were curling in on him as Thorpe made his way towards the main entrance of the Inst.i.tute. Hartford had sent him to find Maxwell Curtis, and Thorpe had an unpleasant feeling that when he got to Curtis's room all he would find would be a small round black lump of... of something.

But as he moved along the corridor, Thorpe began to wonder if he was ever going to arrive at the other end. The ground seemed to be sagging under his feet. The light was going too. The fluorescent strips seemed just as bright when you looked at them, stared at them so hard they left trails across the retina, ghost lights that stayed with you when you looked away. But somehow the light did not seem to reach to the floor, or down the walls. It had lost its strength, was being sucked away.

There was someone waiting for Thorpe at the end of the corridor, at the point where it joined the offshoot that led to Curtis's room. As he approached, he could see that it was Curtis. Or at least, from the grey light falling across the man's body, it was someone wearing Curtis's suit.

But the light did not reach the man's head. It seemed to shy away from it. An inky black stain seemed to spreading through the air above the man's shoulders. Where the head should be.

And Thorpe saw that the light was falling into into that blackness. That the corridor was sloping impossibly down towards the figure. That the walls seemed to be bent round the man. Before he even realised it Thorpe found himself staggering towards the end of the corridor, towards the blackness.' that blackness. That the corridor was sloping impossibly down towards the figure. That the walls seemed to be bent round the man. Before he even realised it Thorpe found himself staggering towards the end of the corridor, towards the blackness.'

He dug in his heels and tried to stop, but his boots skidded across the floor. He scrabbled at the wall, but found nothing to grip. Above him one of the strip lights exploded. He ducked instinctively, but the shower of gla.s.s fragments was cascading along the corridor, not falling to the floor. It was as if the whole place had been up*ended so that sideways was now down. And Thorpe was falling, falling towards the blackness.

At the same time, the blackness was walking slowly towards Thorpe. The stained air moved with it, the corridor warped and bent as if he was seeing it through a lens. He could feel himself being squeezed and crushed, stamped under a giant, invisible foot. Thorpe was on the floor now, sliding along down towards the advancing darkness. Hands reaching out towards him, hands with darkened palms.

Even the sound of his shouts was sucked away, shouts that were turning to screams. Crushed into silence.

The blackness walked on. But Thorpe was gone. Only a small black tone remained a dull pebble, about the size of a golfball. The corridor was empty again, and reality snapped back into shape.

In the Great Hall, Hartford tired of trying to raise his people on the radio. There was no response from the team at the main gate. Thorpe was not answering either. The thirty*minute deadline he had given Nuryshkin was nearing its end, but he was more concerned about what was happening elsewhere.

The ghost, Williamson, was disconcerting him. He stood beside Anji Kapoor, and stared at Hartford. Hartford was tempted to put a bullet through him just to be sure. But he knew it would do no good simply show them how frustrated he was getting. That wouldn't do, wouldn't do at all. He'd been brought in for this mission because of his calm, cool efficiency. Because he was the best. Because he got results and came out with the team intact. Always.

Always up till now.

Still the ghost stared at him, translucent eyes accusing him, stripping away his protective sh.e.l.l.

'Shut up!' Hartford shouted. 'Just shut up. All of you.'

In the nervous silence that followed they all heard the sound of an explosion, followed immediately by gunfire.

Through the chaos and confusion, two creatures walked calm and unworried. Neither of them was human.

The Darkness strode along the warping corridors, making its slow way towards the Great Hall. It had only to wait, of course, and the Great Hall would be drawn to it. But the logic and thought of the human it had once been that it still was, somewhere deep, inside prevailed. For the moment.

At the main entrance, before the smoke of the percussion grenade had cleared, before the exchange of fire between Hartford's depleted forces and Nesbitt's SAS team had settled into the cat*and*mouse chase it would swiftly become, the Doctor strode into the smoke. He looked neither to left nor right; he heard nothing of the melee around him; he saw only the image in his mind of Miriam's body in the Great Hall and of Hartford turning towards Anji.

Fitz was gone, and even if it was not his fault, it was his responsibility. He was not about to let Anji go the same way. His jacket sleeve hung loose, his face was blackened and scratched. His hands were clenched into tight fists at his sides.

One of Hartford's killers lunged out of the smoke, a.s.sault rifle already coming up, finger on the trigger. The Doctor stared point blank at the hot barrel. He didn't hesitate. He grabbed it with both hands and swung. The man on the other end of the gun was smashed sideways into the corridor wall. The man let go of the gun and crumpled to the floor.

The Doctor tossed the gun away. He paused only to grab the man as he tried to stand up, and throw him back at the wall.

The man slumped to the floor, unconscious. But the Doctor was already gone, swallowed up by the smoke.

The SAS had split into three teams. Nesbitt was leading one of them Lansing the second. Beauchamp commanded the third. They had studied maps of the castle facility weeks ago, planned several possible a.s.saults depending on how the enemy force was deployed and in what strength. They had run through each dozens of times in a mock up of scaffolding and tea chests in a hangar at Hereford.

The heads*up displays each of the a.s.sault team could see inside their goggles was linked to sensors that measured how far they had come, slaved to a GPS system to double*check the positioning and the data overlaid on a three*dimensional computer model of the Inst.i.tute. Every one of them knew exactly where he was, where he was headed, and where everyone else was positioned.

At the sound of the gunfire, Hartford visibly flinched. He ran to the floor of the Great Hall and looked out. His expression betrayed the confusion he was feeling.

'You' he shouted across the room. 'Come with me.' The prisoners looked at each other in confusion. 'Naryshkin,' Hartford growled.

Vladimir Naryshkin cautiously approached the door. When he was within reach, Hartford grabbed him and pushed him out into the corridor. 'Come on!' he hissed. 'I don't know what's going on, but I may need some bargaining power. Or a shield,' he added.

He followed the scientist out into the corridor. 'n.o.body else leaves here,' he yelled as he slammed the doors behind him. Smoke was already swirling along the corridor outside the Hall. He set off for the main entrance, pistol drawn and readied.

The smoke got thicker the further they went. Percussion and smoke grenades, he guessed. He could taste the acrid stench of them.

Finally, approaching the Cold Room, Hartford could see a figure up ahead. One of his own, or one of the intruders? He waited, Naryshkin stood in front of him. If there was any gunfire, Hartford was not about to face it himself.

The figure in the smoke was moving purposefully, not checking round or making any effort to avoid being seen. Hartford's own people knew better.

So Hartford levelled his gun over Naryshkin's shoulder.

'Ah, Colonel Hartford.' The Doctor stepped out of the rolling smoke. 'I wanted to talk to you.'

'And I wanted to kill you,' Hartford told him. He aimed the gun, enjoying the moment, savouring the expression of surprise on the Doctor's face. Let it turn to fear and he would be even happier.

But it didn't. Instead another figure pushed through the smoke. Like the Doctor, the figure seemed not to notice or care. It ignored Hartford, ignored his gun, just kept walking.

The ghost. Williamson.

Hartford watched in disbelief as it seemed to melt through the foggy smoke. He turned to watch the figure head on up the corridor. As it went it turned and looked back, as if daring Hartford to shoot him.

Hartford turned too, annoyed that he had let himself be distracted.

Apart from the grey billowing smoke, the corridor was empty. Both Naryshkin and the Doctor were gone. As he looked round in confusion, he heard the click of a lock. The Cold Room. Hartford grabbed the door handle, but he was too late. The heavy door refused to open.

With a scream of rage, Hartford stepped back and fired a full clip into the door. Impossibly, the smoke in the corridor seemed to clear, as if drawn away. Hartford could see a man walking through the smoke. But it was not the Doctor. The Doctor was beside him now, had not slipped into the Cold Room with Naryshkin, but had been standing right with him, unseen while Hartford was watching the ghost.

'This is not good,' the Doctor was saying quietly 'We have to get away from here.'

The man stepped closer. If it was a man. He was wearing a suit, but instead of a head there was just a smudge of blackness. The smoke seemed to swirl into it, light seemed to be sucked in so that the whole figure was indistinct.

'What is it?' Hartford said, for the first time in years hearing fear in his own voice.

'Dangerous.' The Doctor was dragging him away.

But it was an effort. They were both struggling to keep their feet, to keep from falling towards the thing that was striding purposefully towards them. The whole corridor seemed to be bending, warping, around it.

'It's Curtis,' the Doctor shouted. 'What he has become. He'll kill us all.'

'You mean everyone here?' Hartford screamed back. There was a hurricane blowing round them now, smoke rolling past. The armoured door at the end of the corridor was screeching on its hinges as it swung open.

'I mean everyone in the world. But us first. The gravity force will crush us to a singularity if we cross the event horizon. There's nothing we can do about that.'

Hartford was staring down the corridor, his eyes fixed and unblinking. 'Oh yes there is.' He raised his hand, as if checking the time. But the device on his wrist was not a watch. He pressed two of the b.u.t.tons inset on the side, and a series of numbers flared into red life on the watch*face.

30:00.

29:59.

29:58.

'What have you done?' the Doctor hissed. They were still struggling back along the corridor, feet sliding from under them with every exhausting step.

'I'm blowing this place sky*high.' His voice was laced with satisfaction. 'That'll stop it.'

The hinges finally gave out and the heavy door tumbled end over end down the corridor. It whipped past Hartford and the Doctor and crashed against Curtis. Except that it seemed to fall into into him, into the blackness that was his head. him, into the blackness that was his head.

'Blowing things apart won't stop anything,' the Doctor shouted. You really think an explosion can stop that? It will just absorb the energy like it absorbs matter and light.'

Curtis had stopped. For a moment, the door was visible, shrinking, collapsing, crumpling like old paper. The wind died and the smoke rolled on again. Just for a few seconds, as the door was compacted almost to nothing. In those moments, Hartford and the Doctor scrambled back along the corridor as fast as they could.

Then a small black lump fell from the darkness and dropped to the floor of the corridor. The terrible hurricane started again, sucking away the smoke and the sound of explosions and gunfire, and Curtis stepped towards them.

'It hesitated it stopped!' Hartford yelled above the sound, his voice only just audible. They were being dragged back down the corridor again now.

'Only while he absorbed that door, as it crossed the event horizon into the black hole.'

'We can get away. If something large enough goes through.'

'Possibly. Something heavy,' the Doctor shouted back. 'But what have we got?'

'You can stop him?' Hartford was yelling. 'You can stop the killing?'

'If I can get ahead of him. If I have time to think!'

Hartford felt calm now. Calmer than he had since he arrived at the inst.i.tute.

'Tell me one thing, Doctor.'

'I'm not sure this is the best moment,' the Doctor protested.

'There is a time machine here, isn't there? I was right?'

The Doctor turned to face Hartford. 'Yes,' he said quietly. 'Out in the ice. There is a time machine.'

'What will you do with it?' Somehow, maybe because of the intent way the Doctor was looking at him, Hartford knew the Doctor had plan, and he knew the strange man would see it through.

'I'm going to destroy it.'

Now at least Hartford understood what his mission really was, why he had been sent here. 'Then we're after the same thing.'

'I doubt it.'

'Good luck, Doctor!' Hartford shouted.

'What?' The Doctor's expression changed from perplexity to horror. 'No, no that's not the way! Why are you doing this?'

Hartford was pulling off his watch. 'Because, I was sent to do a job. Because I've never hesitated to sacrifice anyone I needed to in order to fulfil my mission.' He smiled thinly, pressing the watch into the Doctor's hand. 'Because perhaps after all the United States themselves are essentially the greatest poem.' Hartford turned away, turned to face the darkness. And ran towards it.

The doors to the Great Hall exploded inwards. Anji leaped to her feet in fear and surprise.

'Ah there you are!' The Doctor was running, Anji didn't like his expression. 'Everyone over here, quickly.'

Everyone was now Anji, George, the Grand d.u.c.h.ess and Holiday. They grouped round the Doctor in confused silence, waiting for him to explain what was happening.

'There is a theory,' the Doctor said to them, 'that black holes were all created at the big bang. That the matter that will one day collapse into a black hole is potentially all around us, just waiting for it to happen.'