'What is it?' she said.

'Go and have some canapés,' he told her.

'Oh,' she said. 'That bad?'

'It is quite bad,' he said.

'What is it?' asked Captain Georgina, coming over with an empty tray in her hands. Archibald also had an empty tray, and it seemed he was going to show her the method for making it full again.

'Oh, nothing,' said the Doctor easily.

Captain Georgina glanced at the screens. 'We're eating up energy,' she said.

'Eating is good,' said Archibald.

'Yes,' said the Doctor. 'But the time loop isn't perfect. It's got a gap in it.'

'So it's more like a horseshoe than a loop,' said Martha, seeing the horseshoe of computers right in front of her.

'Yeah, OK,' said the Doctor. 'Enough with the analogies. So we come speeding round the loop and hit the gap. But the Brilliant has stuff that knows how to bend reality, so it guides us back to the other side and round we go again.'

'And when it's doing that, it restocks the nibbles and brings us back to life,' said Martha.

'All part of the first-class service,' said the Doctor. 'But each time it does that, it needs a bit of power to push it round again. Only it's not a bit of power. It's quite a lot.'

'But we don't have power reserves like this,' said Captain Georgina, her eyes never leaving the screens. 'That's more than a ship this size could ever hope to contain.'

'Ah well,' said the Doctor. 'Depends how you look at it. You know how much energy is freed up just by being stood still in time? You're stuck in the space between moments, so it's like you're idling. Plenty of reserves just because none of you are really moving.'

'So we're OK?' said Martha, relieved. For a moment, she'd thought they were in danger.

'Oh yeah,' said the Doctor breezily. 'Well, kind of.'

'Good,' said Archibald.

'When you say kind of,' said Martha. 'You mean we are in danger.'

'Yeah,' he admitted.

'The energy needed keeps increasing,' said Captain Georgina, studying the screens.

'Does it?' asked Archibald.

'It does,' said the Doctor. 'You see, you're all using up energy while you're stuck here. Breathing, eating, talking, shooting. And coming back from the dead. It all has to come from somewhere.'

'What will happen?' asked Martha. She didn't like how calmly he was taking it. Usually, just a sniff of trouble was enough to get him all fidgety and excited. It also didn't help that behind them the other badgers and humans were enjoying nibbles and polite conversation. She struggled to take it seriously.

'Well,' said the Doctor, sticking his hands in his trouser pockets. 'There'll come a point where the energy isn't there. It'll hit the gap and there won't be enough momentum to get back round again.'

'So we'll be free?' said Martha.

The Doctor jutted out his jaw. 'In a manner of speaking.'

'We won't be free of the time loop?' she asked him.

'We'll be dead,' said Captain Georgina. 'The whole starship will implode.'

'Yeah,' said the Doctor. 'Something of that sort.'

'But there must be something we can do!' said Martha.

'Well yeah,' said the Doctor. 'There's always something. I think I could correct the problem, get us off the sand-bank.'

'So do it!' said Martha.

'Ah,' said the Doctor. 'Still a problem after that.'

'Captain Florence dun't take pris'ners,' said Archibald.

'I'd sort of suspected that,' said the Doctor. 'So that's why it's tricky. If I don't get us out of this, we're all going to die. But if I do, the pirate ship is waiting.'

ELEVEN

The human crew continued to eat canapés, chat and ignore their inevitable doom. Martha couldn't bear even to watch them. She could feel her own heart beating, a sudden sense of herself being alive, of wanting to be alive.

She looked round at the Doctor, busy at the controls of the transmat booth, trying to make it do anything that might help them. He'd used the sonic screwdriver, he'd also used his fists. Nothing seemed to be working. But he kept at it, and she started to think he was just trying to keep himself busy. So he wouldn't have time to think about being trapped. So he wouldn't have to meet her eye.

Martha couldn't help but think back to what the Doctor had said in the TARDIS, when she'd been begging him to bring them here. He'd said there were rules, that they couldn't get involved and they couldn't change anything. And now the two of them were caught up in the same fate as everyone else.

It could be brilliant, flitting through all time and space meeting all kinds of people. But Martha had seen enough people killed, enough terrible, awful things, to know their travels came with a price. And she'd known there was going to be trouble on the Brilliant – that it was going to disappear. The humans and badgers and Mrs Wingsworth had been doomed even before the Doctor set the controls of the TARDIS... And now she and the Doctor were doomed with them.

She made her way over to him. 'You can't get us out of this,' she said. 'Even if you get that thing working.'

He looked up at her. 'Can't I?'

'It would change history,' said Martha. 'And you can't do that. You said there were rules.'

'Rules?' asked Captain Georgina, coming to join them. She seemed to be taking everyone's certain deaths quite easily. Perhaps, thought Martha, it would make her look less effortlessly beautiful if she allowed herself to panic. Or perhaps she just knew there was nothing she could do. Martha's dad always said you should only worry about stuff you actually had any control over. The other stuff would just happen anyway. It was what he usually said when he was arguing with Martha's mum.

'Well, not rules as such,' said the Doctor. 'We have responsibilities. You see, we're sort of from the future and the Brilliant disappeared.'

'I see,' said Captain Georgina.

'You do?' said the Doctor. Martha knew he enjoyed it when people freaked out about time travel.

'I'm fully briefed on the implications of the experimental drive,' said the captain. 'It stands to reason where this technology was leading. I assume you've come back to fix the problem for us.'

'Um,' said the Doctor. 'Yeah, well I was gonna see what we could do.'

Captain Georgina nodded. 'Then we sit and wait it out,' she said.

'Well, yes,' said the Doctor. 'But that's not what Martha was asking. Not can we get out of this, but if we could, then should we?'

'You're telling us it's wrong?' asked Captain Georgina.

'Wrong is bad,' said Archibald, coming over with a tray of blinis.

'So is it wrong to tamper with reality like that?' said the Doctor. 'To come back from the dead?'

'The experimental drive causes problems with causality anyway,' said Captain Georgina. 'Even just starting it up affects what we think of as reality.'

'That's right,' said the Doctor. 'But that's not just true of your clever engine. Look, you change history just by doing anything. Or not doing anything. What you do, what you strive for, every choice you ever make. That's what builds the future.'

'But you only get one go at it,' said Martha. 'Normally, I mean. If you get it wrong, that's tough.'

'You have to deal with the consequences of what you do,' said the Doctor.

'Aw,' said Archibald. 'Do we 'ave to?'

'Yes,' said the Doctor. 'It's called being a grown-up.'

'Sounds really boring,' said Archibald.

'Sometimes it would be good to be able go back and do things again,' admitted Martha.

'You'd think so, wouldn't you?' said the Doctor gravely. 'But it doesn't work like that. It's like telling lies. You can never just tell the one fib, can you? Sooner or later you've got to tell another, just to back up the first one. A week later, you're juggling a whole intricate patchwork of lies on lies on lies. You can't remember what you've told different people, and you're probably not entirely sure what the real version is any more. So it's only a matter of time before someone catches you out or you just plain forget something and it all collapses, boom!'