The Doctor shrugged. 'A little idiosyncratic I admit.' He grinned. 'Sometimes, you know, it intrigues me too.'

'Not the box itself. I'm intrigued to know what is inside it.'

'And I'm intrigued to know what's inside the Grand d.u.c.h.ess's trunk.' He gave her a wave as she glanced across. She glared at him briefly and looked away again.

The Doctor was saved from answering further by the pilot's voice over the intercom asking them to prepare for take*off.

'Perhaps it's Schrodinger's Cat?' the Doctor mused as the plane powered down the runway. The engines strained, the noise building until it was almost deafening. Eventually the huge plane lifted ponderously off the tarmac and skimmed over the ground.

'That trunk of yours must be even heavier than it looks,' the Doctor shouted across at the d.u.c.h.ess as the plane struggled to gain alt.i.tude. 'Maybe it's Schrodinger's weight*lifting kit rather than his cat?'

'I'm afraid I have no idea what you are talking about, you strange man,' the d.u.c.h.ess rebuked him. Her voice was almost lost in the engine noise. But the Doctor beamed at her as if she had complimented him handsomely.

'Well, since you ask,' he said, settling back and adjusting the seat's position so he could recline and steeple his fingers, 'I'll tell you.'

'Oh good,' Holiday said, just loud enough for the Doctor to hear. His tone was unenthusiastic.

'Schrodinger suggested,' the Doctor went on, undeterred, 'that you could put a cat in a box.'

The d.u.c.h.ess seemed unimpressed at the idea. 'There is no cat in my trunk,' she announced loftily.

'Ah,' the Doctor said, with a wink and tap of the nose, 'but there might be. We don't know for certain until we open it.' He beamed at his audience. They stared stonily back. 'You see, what you do is you set up some device you can use a photon of light pa.s.sing through a slit if you really want to make the point. But in Schrodinger's example, the device allows for poison gas to be released inside the box. Or not. There's a fifty*fifty chance and you don't know whether it's happened or not.'

'Why?' the d.u.c.h.ess asked, her face wrinkling even more than usual.

'Well, that's the clever bit, you see. That way you don't know if the cat is still alive or not.' The Doctor frowned. 'Of course, the box needs to be air*tight or you could run into trouble. And if it's air*tight then the cat's rather had it anyway. But leaving that aside,' he said, making a brushing gesture with his hands, 'you are now in the position of having a cat inside a box and no way of knowing if it's alive or dead.'

'But all you have to do is to open the box,' the d.u.c.h.ess pointed out.

'Not take the money?' the Doctor mused. 'You're right of course. But until you do, Schrodinger's Cat is in an "indeterminate state" it's neither alive nor dead.'

'Rubbish,' Holiday told him. 'It has to be one or the other.'

'Well, yes. But you don't know which until the box is opened.'

'I rather suspect that the cat knows,' Curtis said.

'No. Well, yes. Sort of. Look,' the Doctor sat upright suddenly and gestured with frustration. 'Forget the cat for a minute.'

'It was you who told us to poison it,' the d.u.c.h.ess said.

'Yes, fine. Well, anyway it doesn't have to be a cat of course. Though that might affect the poison you choose. Anyway, you open the box and the cat is alive or dead. Can we at least agree on that bit? Good,' the Doctor said after some nodding. 'Now at that moment, a decision has been taken, and the universe splits.'

The d.u.c.h.ess's mouth dropped open.

The Doctor held up his hand. 'Hang on, we're nearly there. Follow me closely now. In one universe the cat is alive, and in the other it's dead. That's what Quantum Theory says. At every decision point, the multiverse gets bigger. It's still finite, although because there have been an awfully huge number of possible differences and decisions, it's an awfully big finite number. I mean you could sit down and count your way through them all. If you had the time.' He leaned back again. 'And a rather more comfortable chair than this one.'

'So...?' the d.u.c.h.ess prompted him.

'So,' the Doctor said, 'Schrodinger used this as an example of just how silly Quantum Theory is. Like you, he said that the cat must make its mind up whether it's alive or dead it can't be neither one thing nor the other. It either is or it isn't. But the irony is that people now use Schrodinger's Cat to explain Quantum Theory rather than rebuke it.' He paused and nodded, evidently pleased with the way the explanation had gone. Then a puzzled frown slowly drifted across the Doctor's face. 'I'm sorry,' he said, 'how did we get on to this?'

It was over an hour before anyone spoke again. And again it was the Doctor. 'Of course!' he exclaimed, his leap to his feet curtailed by the seatbelt across his lap. 'I was asking what's in that trunk of yours.'

The Grand d.u.c.h.ess had been leaning back in her seat, apparently sleeping. Now she opened her eyes and turned slowly towards the Doctor.

'Though I suppose,' he said as she continued to stare at him, 'it's really none of my business.'

The d.u.c.h.ess nodded slowly, and closed her eyes again.

'But,' he said loudly, 'I would be terribly interested to know how dear Alex escaped the firing squad. You're his daughter, is that right?'

'That is right,' she said, opening her eyes again. 'Yes.'

The Doctor sucked in his cheeks. 'I always thought it was odd that they burned the bodies of the maid and the boy. Why not burn them all? Or none of them?' He raised his eyebrows, making it clear he expected an answer.

But the d.u.c.h.ess was getting to her feet and started to walk slowly and carefully back along the aisle. 'You will excuse me,' she said. It was not a question.

'Something I said?' the Doctor asked in an anxious tone.

'Indeed no,' she a.s.sured him. 'I just wish to stretch my legs.'

The Doctor watched her all the way to the back of the pa.s.senger compartment. He watched her open the door to the hold, waved to her as she glanced back to see if he was looking.

As the door closed behind the d.u.c.h.ess, the Doctor turned to Curtis, who was staring out of the window lost in his own thoughts.

'What do you you reckon is in that trunk of hers?' he asked. reckon is in that trunk of hers?' he asked.

20: Off the Scale

Two white*clad figures watched the girl shivering as the snow powdered her face. She had lost consciousness a few seconds ago, and they both knew she would be dead in minutes.

'What do you reckon, sir?' the shorter of the men asked. Captain Mike Nesbitt considered.

'We can't just leave her to die, sir,' Corporal Lansing said. 'She's a civvy. She came with the Yank team, but she's obviously not one of them.'

'She obviously upset them too,' Nesbitt pointed out. 'But we can't afford to look after her. Not with the odds stacked as they are now. And we don't have spare thermal gear.' He looked up from the woman. 'You have a suggestion?'

'Yes, sir, I do.'

Lansing carried the woman. Keeping low, Nesbitt reckoned it was a calculated risk getting this close to the Inst.i.tute's main entrance. But the only sign of anyone around was a dead Russian soldier lying close beside the gates.

'As close to the gate as you can,' Nesbitt said. He had almost to shout above the wind now. The snow was driving at them virtually sideways, which at least meant they were less likely to be seen.

The woman's head lolled and she murmured something Nesbitt didn't catch as Lansing dumped her down into the snow.

'Do it,' Nesbitt said.

Lansing hauled his rucksack off his back and rummaged round in a pocket. He pulled out what looked like a small nail*gun and a plastic wallet. He took the capsule he needed from inside the wallet, loaded it into the device and pressed the muzzle hard against the girl's exposed neck, right at the front of her throat. The sound of the shot was lost as he pulled the trigger.

The girl's neck spasmed, her head knocked backwards by the pressure of the injection.

'What now, sir?'

Nesbitt smiled, feeling the ice cracking round his mouth as he did so. 'We ring the bell and run away. Just like when we were kids.'

'I think you had a rather different childhood from me, sir,' Lansing said as they ran for the nearest cover. They dived behind a drift of snow and watched.

Within a minute, the gates were hauled open from the inside. Two camouflaged figures emerged, guns at the ready, each covering the other as they crabbed forwards over the exposed ground.

'Might be a good way to draw them out,' Lansing said. 'As and when.' The two armed figures from the Inst.i.tute had spotted the girl's body now. They relaxed immediately, and one of them lifted her easily on to his shoulders. Then they disappeared back inside.

'Smooth,' Lansing commented. 'They'll a.s.sume she staggered back this far and pressed the intercom b.u.t.ton, then pa.s.sed out.'

Nesbitt nodded. 'And she won't remember anything to contradict that. Come on, Iet's get back to Base Zero and see what the status is.'

Hartford was livid. A muscle worked in his cheek as he stared down at the woman's unconscious form.

'What happened to Gamblin and Jacobs?' he demanded.

'No idea, sir.' Wences shifted uncomfortably.

'Then find out,' Hartford shouted. 'Now!'

Once Wences had gone, leaving at a run, Bill Thorpe cleared his throat. 'What do you want to do with her?' he asked, nudging Anji's p.r.o.ne body with the toe of his boot.

'Set up a bed in the canteen,' Hartford said. His voice was low and gravelly. 'Keep her warm, and let me know the moment she wakes up. I want her somewhere we can keep an eye on her every second of every minute.'

'One other small matter,' Thorpe hazarded.

'What?'

'We have a plane heading this way. About ten minutes out.'

'If you must know, Doctor, it was because Alexei was not there.' The Grand d.u.c.h.ess said.

'I'm sorry?' The Doctor looked up. He had been dozing, his brain taking the opportunity of some peace and quiet to run through everything he knew about Curtis, the Grand d.u.c.h.ess, the events at the Auction House...

'That is why they claimed they burned his body. They could never produce it.'

'Ah,' The Doctor nodded. 'Well, I don't think they actually intended ever to produce any of the bodies.' He glanced out of the window. 'I think we're almost there,' he said as the engine sound deepened slightly. Snow was spattering past the windows as they lost height.

Beside the Doctor, Curtis was struggling to his feet. Across the aisle, Holiday was already standing.

'Shouldn't you be strapping in, restoring your seats to the upright position, that sort of thing?' the Doctor asked.

'The pilot will be concerned that he can't land on the short runway at the Inst.i.tute,' Curtis said as he pushed clumsily past the Doctor. He seemed tired and ill from the journey.

'Well, it's a thought,' the Doctor admitted. 'The weather doesn't help, of course.'

'And what will you tell him if he says he cannot land?' the Grand d.u.c.h.ess inquired. 'What if he says it would endanger our lives?' There was a hint of anxiety in her tone, and in her eyes.

'It is his own life he needs to worry about first and foremost,' Holiday said as he followed Curtis towards the c.o.c.kpit.

'I bet you're glad you asked,' the Doctor whispered loudly to the d.u.c.h.ess.

She raised an ancient eyebrow, the wrinkles round her eyes twitching with the effort. They could clearly hear the sound of the wind and feel it buffeting the plane as it flew ever lower.

'No boiled sweets,' the Doctor observed in a melancholy tone.

Base Zero was a collection of white tents in a hollow close to the Inst.i.tute but out of sight behind a low hill. Around the edge were parked the various snow*cats and other vehicles that the SAS team had used to get there. Inside the largest of the tents was a mobile command centre. Lightweight folding chairs stood around lightweight folding tables on which laptops and other equipment hummed and gleamed.

It took Nesbitt only a minute to get updated. There was a plane approaching a large cargo plane. But nothing was scheduled so far as they knew. His first thought was that it was the American incursion team bringing in reinforcements. That was an unwelcome development and would make his job all the more difficult. Especially as there was another factor that now came into play.

'He was quite insistent, sir,' Private Phillipps told Nesbitt. 'The last gravity wave readings were in the region of a few nanometres. These were off the scale.'

'And centred here?'

'Near as they can tell. Within a hundred kilometres. G.o.d knows what they're up to in there.'

Nesbitt nodded. 'How long till the plane lands?'

'Maybe five minutes. We'd hear them if the wind died down for a moment.'

'No time to take the Inst.i.tute before it gets here, then.'

Lansing was shaking his head. 'We don't know it is reinforcements,' he pointed out. 'Maybe Charles can tell us.'

'Good idea.' Phillipps was already back at his equipment.

In seconds the plummy voice of Corporal Charles Beauchamp crackled through the speakers by the comms laptop. 'Plenty of activity, sir. Just in the last couple of minutes. Doesn't look like they're rolling out the red carpet though.'

'So what does it look like?' Nesbitt demanded.