'Is that an "ah, I’ve found something interesting," or an "ah, we’re all going to die?’' '

'Can’t it be both?'

Amy gave the Doctor the look she’d been finding increasingly useful these past few months. It was an elevated left eyebrow look, one which clearly said, ‘are you quite mad?’ Of course, she’d long ago realised that the answer to that question was a definite yes, but that didn’t stop her developing eyebrow-raising to a fine art.

Currently leaning over the central console, the eccentric time traveller was not exactly inspiring confidence in his work. Holding a handful of exposed wires in one hand and something that looked very much like a kazoo in the other, she couldn’t remember ever seeing him look more like a mad professor.

'Look, can you fix it or not?' she demanded.

For perhaps the third time in as many days, the TARDIS was refusing to play ball. The Time Lord’s repeated attempts to get the engines running again were proving thoroughly unsuccessful, and Amy was beginning to lose her patience.

'It’s not that simple,' the Doctor explained. 'The TARDIS isn’t just something you fix, she’s a living thing. You have to... persuade her to start working again.

'How do you...' she began, before holding up a hand. 'No, forget I asked.'

Emerging from the corridor, Rory entered the room dressed in a pair of swimming shorts, scrubbing at his head with a towel. Drips of water were scattering off him, forming a small pool around his feet.

'Watch the wiring!' the Doctor hissed, as his companion approached the console.

Stepping backwards from the Doctor’s work, Rory took up a perch a safe distance from the other two, leaning against one of the railings that surrounded the centre of the control room.

'Still broken I take it?' he asked.

'Yep,' Amy replied. 'How was your swim?'

'It was going really well until the fish turned up.'

Amy raised the other eyebrow. 'The fish?' she asked.

'Yes,' Rory nodded in reply. 'There’s a load of fish in the swimming pool.'

Amy looked confused. 'Then why did you get in?' she asked.

'Well they weren't there when I started. Then twenty lengths later, thwop, fish.'

'I don't believe you,' she replied.

'See for yourself.'

'No. I don't believe you could manage twenty lengths without passing out.'

Rory ran his fingers through his hair, then flicked a handful of cold water at Amy. Squealing in protest, she stepped away from her husband.

'What do you mean, thwop?' she asked a moment later.

'Thwop. That's the sound the fish made when they appeared.'

'Aha!' exclaimed the Doctor, suddenly taking an interest. 'What kind of fish?' he asked, clambering out from underneath the TARDIS console.

'I don’t know, blue?' Rory replied. 'Does it matter?'

'Possibly not, but a single Malengan trout provides the same power output as a type three fusion reactor. Just one of those could have provided the jump-start we needed right now.'

'Want to check it out?' Rory asked.

'Not much point, a Malengan fish would have also turned you to atomic residue before absorbing you through its gills for food.'

'Oh,' muttered Rory. 'Sorry I couldn’t be of more help.'

'The question is,' the Doctor continued, barely listening, 'why the swimming pool? Why the fish, and above all else, how and why did they thwop there?' He turned to the console and began feverishly making calculations on the main computer.

'Think about it,' he instructed. 'Every planet in the universe orbits their star at a staggering speed. Now each of those stars orbits the centre of their galaxy. Those galaxies are hurtling through space at an unimaginable rate. The TARDIS is one of the most complicated devices in the universe, but even so I still sometimes struggle to hit the planet I'm aiming for. And you're telling me a shoal of fish just happened to thwop into the middle of a tiny blue box somewhere in the universe, and not only that, they just happened to land in a swimming pool? No, the fish, the pool, the kazoo... It all just seems a bit too improbable.'

'A theory?' Amy asked.

'A theory!' the Doctor exclaimed, raising a finger in triumph. His two companions looked at each other for a moment with apprehension, but decided to listen anyway.

'Now then,' he began, 'there are moments in time that are fixed; unchangeable times where whatever happens, happens. Times that the universe and everything in it rely upon. Then there are the fluid moments where events can be changed. Slippery moments that act like the lubricant in the gears of the universe.'

'We know Doctor, you’ve told us this before,' Amy commented. 'And more than once, I might add.'

'But then there are the other moments,' he continued. 'The moments where time and space collide in chunks of wibbly wobbliness and bounce off in all different directions. These are the moments where events mean nothing, where cause follows effect before following cause again. Probable becomes improbable, unlikely becomes likely.'

'But that doesn’t make any sense,' Rory pointed out.

'Of course it doesn’t, that’s the whole point. They’re the fleeting moments when you catch a glimpse of someone in the corner of your eye who can’t possibly be there. When you put down your keys for just a moment and then find them in another room two hours later.'

'That’s just life playing tricks on you,' Amy argued. 'It’s not real.'

'I thought that once, then I met a man named Schrodinger,' the Doctor replied. 'Poor fellow. A lovely man he was, shame about his cat.'

'What cat?' Rory asked.


After a brief pause made it clear that the Doctor had no intention of elaborating, Amy stepped back in to continue the conversation.

'So this is one of those moments?' she asked.

'Might be, it’s very difficult to tell,' the Doctor replied. 'It would explain why the TARDIS can’t figure out where we are, and why I can’t get her moving again.' He paused and scratched at his chin. 'Do you know where your keys are?' His fingers clattered across the surface of the TARDIS console and a screen blinked into life.

'Right then. According to this, we’re stuck in a bubble of improbability. It’s very difficult to be certain of anything right now, but all I know is that right now outside that door could be absolutely anything.'

Rory raised a finger. 'And that’s different to normal, how exactly?'

'I mean anything,' the Doctor replied. 'It could be a world made of jelly, a jelly made of worlds. It could even be something completely non-jelly related.'

'Are we in danger?' Rory asked.

'The TARDIS should protect us from the majority of its effects,' the Doctor replied.

'Even so, the odd thing will still manage to slip through.'

'Like the fish?'

'Precisely. And the kazoo.' He lifted the offending instrument to his lips and blew an unpleasant rasp.

'So why are we stuck? You say these things happen all the time.' Rory asked.

'They do, the chances of one interfering with the time stream are infinitesimally improbable. The problem is, improbable things are quite likely round here.'

'But how can you be sure?'

'An experiment!' the Doctor exclaimed.

Rory rolled his eyes. Despite his fondness for the Doctor, he was never particularly enamoured with the time-traveller’s delight in experimentation. Things had a tendency to turn out...surprising.

Clambering out from under the console, the Doctor finally emerged with a small cloth bag, then extended it to Amy. 'Close your eyes,' he said. 'I want you to reach inside this bag at random and pull out a billiard ball.'

Amy shrugged and dipped her fingers into the bag. After a moments fishing around, her fingers retreated, a black eight-ball clutched triumphantly in her grip.

'Ta-dah!' she exclaimed. 'Why have you got a bag full of snooker balls, anyway?'

'Billiards, not snooker,' the Doctor corrected. 'And I don’t,' he added, turning the bag inside out.

'The bag’s empty.'

'I don’t understand,' Amy responded, mirroring Rory’s feelings precisely.

The Doctor buried his head back in the console, snapping levers backwards and forwards and jabbing at buttons ferociously. 'It means,' he replied finally, 'that our thoughts and expectations are having an impression on the probability matrix. It means anything you say, do or even think can have an impact on reality itself. Above all else, it means trouble.'

'I thought you said we were safe?' Amy pointed out.

'The TARDIS shields should be protecting us, but probability seems to be breaking down at a local level, so I can’t exactly be certain.'

'So what can we do then?' Rory asked.

'There’s a way out, there must be a way out. If there’s one thing I’ve learned over the centuries there’s always a way out. So sit quietly and let me find it.'

He paused.

'Oh' he finally added, 'and try not to think about anything. Especially not anything really, really dangerous.'

He paused again.

'And Rory, go put some clothes on.'