Witnesses to what? Was it just out for revenge for getting an axe swung at it?

Was it after something else that Rory couldn’t begin to imagine?

His mind was all over the place. It was hard to focus. That was shock and the panic response. He forced himself to concentrate. He needed to listen.

Hiding behind the tree, the only way he could tell how close the green thing was, was to listen, but he couldn’t hear anything over his own panting. He held his breath.

It was a considerable effort. He held on, and listened. It felt like his eardrums were going to burst.

After a few seconds, he heard deep, crunching footfalls in the snow, the steady march of the towering monster. It was drawing level with his hiding place.

There was nowhere else to hide. Snow was all around, a white backdrop against which he would stand out, no matter where he went. Trees were no good. Sooner or later, you could walk around a tree.

There were no boulders, no bushes, no holes in the ground.

He heard the crunching footsteps again, and a wheeze of respiration to go with them. It reminded him of his own need to exhale. He eased out the breath he had been holding in, trying to do it soundlessly. He so wanted to greedily suck in fresh air.

The green thing appeared about twenty metres to his left, side on to him. It emerged from between two trees and stood still, slowly scanning to left and right.

Rory, gently and ever so slowly, melted himself back around the tree trunk he was sheltering against, putting it between him and the creature.

It turned and looked his way.

How could it have seen him? He was barely moving. The thing looked like a giant, humanoid reptile. Did reptiles have acute sight? Hearing? Did they have other senses? How did they hunt? He had a feeling that he’d once read something about crocodiles having amazing night vision.

Rory realised that terror was flooding his mind with jumbled thoughts. Nothing he was thinking about really mattered. He had to find an escape route. What the Doctor would call a ‘wise exit strategy’. What Amy would call a ‘not at all stupid bit of proper running away’.

Amy.

Rory knew he simply had to see her again. He wasn’t going to let a giant shambling lizard kill him in a snowy wood for no good reason. His wife would never let him hear the end of it.

He broke cover and started to run again, this time in a path perpendicular to his original route. A hasty glance over his shoulder told him that the green thing had spotted him. It had turned to blunder after him.

Had it detected movement? Heat?

Heat made a kind of sense. He clung on to the notion.

Why wasn’t it shooting? Why didn’t it fire its horrible gun? It could just bring him down and save itself the effort of chasing.

There seemed to be only three possible answers to that. It had run out of shots, which seemed unlikely.

That was one. The second was that he was out of range.

The third was that it wanted him alive.

‘Slow down!’ hissed Amy.

The Doctor was leading the way up the snowy track into the woods with the sort of indefatigable and boundless enthusiasm only he could muster. She scrambled to keep up.

‘Are we taking him with us?’ she asked.

They both glanced back.

Arabel was following them, with the young man in tow. Samewell was a pretty good-looking bloke, Amy had to admit. He was fresh-faced and cheerful. He seemed trustworthy. He was having an argument with Arabel as he pursued them up the lane.

‘It’s a Cat A crime,’ Amy heard him saying. ‘A Cat A crime, Bel! What are you doing with them?’

‘I’m looking for Vesta.’

‘But you let them out, Bel! What will the Elect say?’

‘I don’t know, Samewell? Are you going to tell him?’

‘I ought to!’ declared Samewell. ‘Come on, stop and talk to me! Think about this! You’re consorting with conjury!’

‘I’m looking for my sister,’ Bel replied. She kept walking, pulling her long skirts up a little so they didn’t get trodden into the snow.

The Elect will find Vesta,’ said Samewell. ‘Where is your patience?’

‘Shut up, Samewell.’

‘Those who are patient, they provide for all of the Plantnation,’ he said.

‘Don’t quote Guide’s words at me!’ Bel snapped.

‘I think we’ll let him come with us,’ the Doctor told Amy.

‘Because if he goes back, he’ll tell them where we’ve gone?’ asked Amy.

The Doctor nodded. ‘I don’t think he’s going to overpower us singlehanded,’ he said.

‘I think he’d like to overpower her singlehanded,’

said Amy.

‘What?’ asked the Doctor.

‘He fancies her,’ she replied. ‘It’s obvious.’

‘Because they’re arguing?’

‘Why else did he follow us? He could have just raised the alarm.’

The Doctor frowned thoughtfully and nodded.

‘Keen insight, Pond. The mysterious operation of the human heart. Good job.’

He came to a halt. They had climbed quite a way into the skirts of the woods. Would Be, Bel had called it. The Spitablefields fell away behind them. They could see the village of Beside and, south of that, the glint of sunlight on the glass roofs of the heathouses.

‘Would Be,’ said the Doctor, looking at the shadowed trees and their bright mantles of snow. ‘The original Morphans looked at this world, and imagined how it would be. Like a declaration of intent.’

‘I thought she was saying “Wood B”,’ said Amy.

‘She probably is,’ replied the Doctor. ‘That’s probably all it was originally. A territorial designation.

Wood B. The hospitable fields. Even the name of the settlement. Hmmm. What’s the betting?’

He turned to Bel.

‘Is the third plantnation called Aside?’ he asked.

‘Yes,’ she replied.

‘How did you know?’ asked Amy.

‘Oh, a wild guess. Aside, Beside and Seeside. Sites A, B, and C.’

‘Ah,’ Amy smiled. ‘So Seeside isn’t beside the sea, then?’

‘I imagine not, though I do like to be beside it,’ said the Doctor.

They walked on for a moment, not talking, listening to the breathless hush of the wood and the crunch of their footsteps and the half-audible bickering coming from behind them again.

‘What is Hereafter?’ Amy asked.

‘It’s a colony world, a human colony world,’ said the Doctor. ‘Late expansion, Diaspora Era. Think of the name, Morphan?’

‘Like orphan?’

‘Yes, but also referencing the terraforming or terramorphing processes these settlers were supposed to perform. To colonise a suitable, Earth-like distant world and make it more Earth-like.’

‘Earth-ish?’

‘Indeed.’

‘Where’s the real Earth?’ Amy asked.

The Doctor shrugged. ‘Somewhere in the past. I think the Earth and the solar system are gone. The end of their natural lifespan. Humans had to find somewhere else. Think about the name Morphan again.’

‘How long have they been here?’ asked Amy. She had been to times when the Earth had been abandoned before, but the idea that the world no longer existed seemed especially melancholy.

‘Generations,’ replied the Doctor. ‘Many generations.

Twenty-seven, she said. Lifetimes of backbreaking toil and hard living. It takes a long time to shape and tame a world, even an Earth -ish one. All their labour, all their effort - the Morphans will never get to enjoy it or benefit from it. It’s simply for the benefit of the future generations.’

‘So what exactly is the problem?’ asked Amy.

‘You’re worried about the snow.’

‘The process has gone wrong,’ said the Doctor, quietly enough that neither Bel nor Samewell could overhear. ‘For some reason, the terraforming programme has abruptly failed. Hereafter is becoming less and less Earth-like. The Morphans came here to plant a nation, but now they’re simply going to die out.’

‘Why?’

‘I don’t know,’ said the Doctor.