Ixyldir turned his head slowly and looked at Ssord.

Then he looked back at the Doctor.

‘Lord Ixyldir,’ said the Doctor. ‘According to your scans, how many new heatprints have appeared in addition to the existing human population here?’

The Ice Lord permitted himself a glacial pause before replying. ‘One hundred and fifty,’ he replied.

‘Down here!’ Amy yelled.

She was leading the way, her duffel coat flying out behind her. Samewell and Arabel were running to keep up.

‘They’re coming after us, Amy!’ Bel cried.

Amy looked back. Thirty-five metres behind them, two Ice Warriors had appeared on a gantry platform and were following the three humans onto the grilled shipskin bridge that arched across a vast turbine chamber. In the past five minutes, Amy and her companions had been chased through four large compartments just like it. Each time they had emerged onto a platform or bridge at a different level. Each time, they believed, briefly, that they might have finally shaken off their pursuers.

But each time, the Ice Warriors had appeared, relentlessly searching and hounding.

The bridge they were currently crossing spanned a large chamber at a particularly high level. Several other walkways criss-crossed the chamber at different levels below them. Far below the bridges, at the bottom of the yawning drop, there was a huge cavity that looked like the bowl of an active volcano. Molten fire seethed and roiled down there, an abyssal well of flames. They could feel the heat rising through the space of the compartment. High overhead, unfurled like sails, titanic thermal vents were arranged to conduct and direct the heat.

‘We can’t run for ever!’ Samewell yelled.

‘Watch me!’ Amy cried.

Arabel let out a shriek of despair. ‘Look!’ she yelled.

Amy skidded to a halt. They were about halfway across the long, railed walkway. Three more Ice Warriors had just appeared at the other end of the span.

Ice Warriors were closing in from both sides.

They were trapped in the middle of the bridge.

There was nowhere to go.

‘What do we do?’ asked Samewell.

‘We surrender, don’t we?’ Arabel said.

‘No!’ said Amy firmly. ‘They won’t take us alive.’

She looked around. She looked up. She grabbed the guard rail, leaned out, and looked down. ‘We jump,’ she decided.

‘Are you mad?’ asked Samewell.

‘To kill ourselves so they can’t capture us?’ asked Arabel.

‘No!’ replied Amy. ‘What do you take me for? I’m not going to stupid well kill myself! We jump down onto that!’

She pointed.

The closest of the bridge spans beneath them was only a few metres below. They were almost directly above the point where two bridges intersected.

‘We’d never make it!’ objected Arabel. ‘We’ll jump and miss!’

‘We won’t miss!’ replied Amy. She started to hoist herself up over the rail.

‘It’s too far!’ Samewell cried.

Amy got her heels on the edge of the walkway, holding the handrail against the small of her back. She stared down. It did look far too far. It looked ridiculously too far. It was like jumping off a tightrope and hoping to land on another tightrope.

‘We can do it!’ she insisted.

She looked at them. Arabel and Samewell were clutching each other and staring at her in dread.

‘Come on!’ Amy yelled. ‘Look how close they’re getting!’

Bel and Samewell looked around. The two Ice Warriors behind them were approaching rapidly. The three coming the other way weren’t so close, but there wasn’t a lot in it.

‘Any better ideas?’ Amy yelled. ‘No? Then come on!

Now!’

Uttering moans of reluctance and fear, the two Morphans scrambled over the rail next to her.

‘It is so high, I fear I shall faint,’ said Bel.

‘Try your best not to,’ said Amy. ‘OK. OK. I’ll go first. I’ll show you how it’s done. OK.’

Perched, they looked at her.

‘OK, I’m going,’ said Amy. Her hands didn’t seem to want to let the handrail go. It really was a very, very long way down. What had she been thinking? She couldn’t make that. It was crazy. It was crazy, crazy talk. Even if she did jump, and didn’t miss the bridge, she’d break a leg, or a neck, or something else that she was fairly unwilling to damage.

‘A-Amy?’ Bel said. Her voice was trembling. ‘Amy, are we going to do this?’

‘Yes. We are. Hang on. OK. OK, I’m… OK. Ready?

I’m ready. OK. Here we go.’ Amy swallowed hard.

‘Actually,’ she said, ‘I think it might be a bit too far after all.’

She looked around at Bel and Samewell, in time to see an Ice Warrior reaching a huge, green pincer-hand out to grab them.

‘Geronimo!’ she yelled.

And jumped.

‘Rory?’ Vesta asked. ‘Rory, what are you doing?’

Rory didn’t reply immediately. He was moving around the assembly hall, shifting benches and knocking on wooden wall panels.

‘Not green?’ he asked. ‘The thing you saw? In the woods? “It”? It wasn’t big and green?’

‘It was a monster,’ Vesta said. ‘A big monster with claws and red eyes, but it was nothing at all like the green thing you described.’

Rory tapped his way along a panelled wall, listening.

‘It’s fair to say,’ he said, ‘that I haven’t been entirely up to speed on this situation since I arrived. But now I really don’t know what’s going on. I mean, I don’t have a clue. Is it possible that we’re in the middle of some sort of war that we didn’t previously know about?’

‘I don’t know, Rory,’ said Vesta. Every flash and boom from outside made her jump and look towards the windows. The night sky was underlit orange with flame from burning woods. The noises of battle were getting closer.

‘What are you doing?’ she asked again.

‘I’m looking for…’ Rory began. He dropped his hands and stood back from the beam he’d been examining. He shook his head. ‘I don’t know what I’m looking for,’ he said. ‘The Doctor turned this room into some kind of communications station. A receiver. I just thought that… if he could turn it on from his end, I should be able to do the same here. There should be controls, hidden somewhere, I suppose. Perhaps boarded up or panelled over because the Morphans didn’t know what they were for. I thought I might be able to find them.’

Vesta shrugged. ‘Guide only knows,’ she said. She cleared her throat. ‘Rory,’ she said. ‘I think that I want to go and hide in the barns with the others. I think that’s the safest place.’

He looked at her. ‘Yes, that makes sense,’ he said.

‘You should do that. Do you want me to take you there?’

‘No, I can find my way. Will you be all right?’

‘Yes, I…’ Rory’s voice trailed off. He looked at her with such intent, she laughed and shook her head in confusion.

‘What?’ she asked.

‘I said I was looking for the controls, and you said…?’

‘I don’t know, Rory!’ she said.

‘You said, “Guide only knows.’” He grinned. ‘I’m not thinking straight. I wanted to try and get this place running, so that once I had got the Guide, I had a way of sending it to the Doctor. But I can kill two birds with one stone. Your Guide Emanual will tell me how to operate this station. It stands to reason.’

He turned and walked towards the rear doors of the assembly hall. Vesta ran after him, her skirts gathered up.

‘Are you really going in?’ she asked. ‘Into the Incrypt?’

‘Yes,’ he replied.

‘Even though you are not one of the Beside council, and permission was expressly denied to you?’

Still walking, Rory gestured towards the hall windows and the rumbling flash of the onslaught.

‘Hello?’ he said. ‘Bigger picture?’

‘But—’ she began.

‘Vesta, I think that the solution to all the many and troubling problems plaguing us right now are in that room. The Doctor thinks so too. So I’d better get on and find them, because the alternative isn’t really very pretty.’