'Why, King George, of course,' replied the man. 'The third King George. How could you not know that, sir?'

'Course he is,' said the Doctor tapping his forehead. 'Must be the cold - icing up the brain circuits.'

The man looked astonished, and quickly skated off.

'Old Georgie-boy - I knew him well. Thrashed the French in the Seven Year War, pounded them again at Waterloo... and made a terribly good lemon meringue pie.' The Doctor frowned. 'Or was that Gordon Ramsay? I never could remember.'

'I have no idea what you're talking about,' said Mai. 'You really are a very strange man.'

'How nice of you to notice,' grinned the Doctor.

Mai looked at him askance, then she laughed.

'Gift shop!' cried the Doctor. He'd spotted a man selling souvenirs. 'Woo!'

They skated over to the stall and browsed the goods.

'What's this?' asked Mai, holding a small object up to the light.

'It's a thimble.'

It had Frost Fair 1814 painted on the side in delicate copperplate.

'A what?' she asked, confused.

'It's a long story and it involves darning socks. Not very useful for someone from 5113. Want one?'

'If it's not very useful, why would I want one?' she said, handing the thimble to the Doctor.

'Sometimes there's nothing as nice as something that's totally useless,' he said. 'But I'm all out of gold guineas anyway.'

Then something caught Mai's eye, and she pointed through the crowd. 'What's that?'

'Looks like an ice sculpture to me.'

'A sculpture made of ice? Wow!' She skated off to take a closer look.

'Are you going to buy that, sir?' asked the souvenir seller, frowning. 'This isn't a museum.'

'Quite right,' said the Doctor. 'Trouble is...' He rummaged in his pocket. 'I've got no...' Then his hand brushed against the psychic paper. 'Ah!' An idea struck him. 'I'm from His Majesty's commission for...' He held up the paper. 'Thimble inspection...'

***

It stood twelve feet tall, a vast icy sculpture as beautiful as anything Rodin ever chiselled. It was delicate, translucent, and crudely human in shape - yet its edges were sharp, squared off, unfinished. Its bearded features were more like those of a Greek god than a man. And Mai felt, despite its beauty, that there was something frightening about it.

She pulled her scarf tighter around her neck. She was positive the temperature had fallen even further. Then she remembered she still had the Doctor's thermometer.

'Minus twenty-three,' she murmured, surprised. 'It is getting colder.'

Intrigued by the huge statue, Mai moved in for a closer look. There was something strange about the ice they'd used to sculpt it - it looked more like frosted glass - so she reached out and touched it.

As her hand made contact, she let out a cry of pain. It was as hot as an oven.

'What the..?'

More than that, for a moment, her hand was actually stuck to the sculpture, as the figure emitted a strange red glow, like blood pulsing through a transparent vein.

Mai yanked her hand away and an icy coldness gripped her. She spun round, bashing into the Doctor as she did so. 'That thing's red hot!' she cried.

He quickly pushed a small object into his jacket pocket. 'Don't be ridiculous, Mai.' The Doctor reached out. 'That's nothing but a... aargh! You're right!' His hand also stuck to the sculpture for a moment before he summoned enough strength to pull it free.

She shook her head despairingly. 'What is it with men? Just like little kids - they won't be told.'

'Did you see that?' asked the Doctor in a hushed voice, suddenly serious. 'It glowed.'

'That can't be manmade,' said Mai. 'Aliens?'

'Well, if it's not, it's the hottest lump of ice I've ever known. You wouldn't want that floating in your orange squash.'

'Did you notice, when you touched it though, it made you go really cold? I know it's cold generally, but that made me even colder.'

'Right!' trumpeted the Doctor. 'Everything around is growing steadily colder, while this is getting hotter.'

'So it's taking the warmth out of everything?'

'From you, from me... from the very Earth itself.'

They stared at one another in silence.

'What are we going to do? Find an ice pick?' offered Mai, only half joking.

'We need to communicate with it. And who better to do that than yours truly? I get on rather well with aliens.'

The Doctor cleared his throat.

'Now listen here. My name is the Doctor. And I demand to know what business you have here on Earth!'

Silence.

'Shall I get that ice pick?'

'This is serious, Mai.' The Doctor frowned. 'There's only one thing for it. Here goes.'

Before she could stop him, he'd placed both hands on the surface of the huge figure.

'No, Doctor!' yelled Mai. 'Don't be stupid!'

'Stand back!' he cried. 'It needs my energy to speak, to move... to live.'

'But you'll -'

The Doctor silenced her with a shake of his head.

'Who... are... you?' he hissed, addressing the statue.

The strange being before them glowed again with a deep red light. Then with a sinister grinding sound, it slowly lowered its icy head to look down at the Doctor. Two balls of fiery light burned in the centre of its face.

'Where are you from?' demanded the Doctor, his energy already dwindling.

The alien spoke.

'I am Masoon,' it said in a thin yet deep voice, close to a whisper. 'Of the Hyban.'

'The Hyban?' repeated the Doctor, shutting his eyes. 'Where have I heard that name before?' His brow furrowed in thought. 'Of course! The Hyban. Peaceful race, and one of the Universe's only true endothermic life forms. They draw in heat from their surroundings to fuel themselves. Ironically, some call them the Frozen.'

'My planet is dead. An icy world orbiting a collapsed star,' said Masoon. 'The Hyban have travelled across the galaxy to find new sources of power. My journey finally brought me to this star system. I sensed the vast fires raging on this tiny planet.'

'Of course! The Human race is on the brink of an industrial revolution. Mountains of coal being burnt at an incredible rate to fuel thousands of new machines.' He paused. 'And nowhere more so than in London.'

Mai's expression darkened. 'He's sucking out all the warmth, just to stay alive. That's why the temperature's falling so fast!'

'Right,' the Doctor managed through chattering teeth. 'And that's just the beginning...'

'But everyone will die. There'll be an ice age.' Mai glanced at the thermometer and shivered. 'Minus thirty!'

'There's no time to lose!' And summoning up all his strength, the Doctor pulled himself free from Masoon.

'Are you all right?'

He nodded, but before he could say a word, the creature raised its two vast, translucent arms high in the air, and lunged forward.

'Doctor, look out!'

Continued...