Georgie and Portia’s faces slumped with displeasure.

‘We don’t want it,’ they said. There was a dangerous edge to their voices. Portia’s hand moved towards what looked like a water pistol. Their father laughed pleasantly.

‘Yes, you do!’ he replied. ‘Come on back to the party, poppets. You wouldn’t want to upset Mr Preen and the others, would you?’

‘Yes –’ Georgie began, but it was no good. Tosh, using his considerable girth, shepherded the children out of the playroom, Portia hiding the water pistol in the folds of her skirt.

A huge, white cake stood on a trolley in the centre of the party. Ribbons of pink and blue icing decorated its many layers. Everyone stood expectantly around it, as Mrs Puddingham-Pye stuck little pink and blue candles on to its surface.

‘It doesn’t actually look too bad,’ said Archie. A shadow loomed over his shoulder.

‘I take that as the highest compliment, ha ha,’ whispered Preen in his ear. The man was just behind him, grinning wickedly.

Archie stepped away in alarm. ‘I know what you are, and what you’re up to,’ he said, trying to sound braver than he felt. ‘And I’ll stop you.’

‘Oh no, young man, ha ha. I don’t think you do know, on either count. Also, I believe you are lacking a certain, shall we say, family heirloom? A jewel of some importance, ha ha!’

The Treeheart! He knows about it, thought Archie. Preen must be the Mirk! The dentist saw Archie’s look of shock and his smile curled cruelly. Archie backed away, filled with terror. He was trapped, surrounded by strange faces in an unfriendly house. His head ached suddenly and sweat was forming on his brow, just like the first time they had seen the monster in the forest. It’s too powerful! I can’t do anything to stop this!

At that moment, Mrs Puddingham-Pye clapped her hands.

‘Attention, everyone,’ she said, gazing imperiously around at her guests. ‘It’s time for birthday cake. And what a masterpiece of wholesomeness it is! Made from ground coconut fibre, grass seeds, grated turnip and other delicious ingredients, sandwiched together with Puddingham-Pye’s patented Cremoliant synthetic cream and bedecked with toothpaste icing swirls. Completely, delightfully, sugar-free! Now, which of my two angels wants to light the candles?’

‘Me,’ said Portia. She stepped forward and pulled the water pistol from its hiding place and aimed it at the cake.

FWOOOOOOOOOOSSSH! A blast of fire, not water, swept across the room, enveloping the cake and incinerating it in an instant, toothpaste swirls and all. Portia calmly turned off the device and smiled triumphantly at the foaming slag heap that had once been a cake.

‘My birthday present to myself,’ she said, blowing across the pistol’s smoking muzzle. ‘A flame-thrower of my own design. I call it the Deathbreath 3000.’

‘She made that at after-school club,’ said Mrs Puddingham-Pye, proudly, to the hushed, open-mouthed guests, as her husband gaped with embarrassment. ‘She was top of her class in science this term, dear thing, and we almost got through the year without any teachers getting injured. We’re so blessed.’

Archie wasn’t listening – his fear had suddenly vanished. And where was Edward Preen? As soon as Portia had unleashed the Deathbreath 3000, the man had disappeared. Then Archie saw him, standing – hiding? – behind a marble pillar, the crimson light of the dying flames reflecting from his perfect, smooth face. Perhaps the cake going ka-blam had upset him.

Whilst the guests warily inspected the cinders of coconut fibre and smouldering turnip, Archie decided this was a good time to make his escape. He tiptoed to the front door, but found the exit was guarded.

‘Leaving already, Urchin?’ Mrs Puddingham-Pye had got there first. ‘We haven’t even started the party games yet,’ she said, raising an eyebrow.

‘I’ve had a lovely time,’ lied Archie. ‘But I really must be going. I had a nice chat with the twins.’ He gave her a meaningful look. The woman’s eyes flashed.

‘I hope you learned something … useful,’ she said. He knew she couldn’t talk about Preen. All she said was: ‘If you need me, boy, you know where I am.’ She quietly opened the door and let him slip away.

Archie had never thought he’d find himself on the same side as the Puddingham-Pyes! He wouldn’t ever be able to properly trust them, but it seemed, for now, there was a kind of truce in place.