The ball was about the size of a human head and made from pure sparkling crystal from Ancient Greece. It rested on a small circular stand made out of white sheep bones – at least, I hoped they were sheep bones. To one side there were several white knobs shaped like tiny human skulls.

‘Get on with it, then!’ said Aunty Grizz.

I closed my eyes and tried to remember what Mrs Winkle had taught me about operating a crystal ball. I spread my hands over it, took a deep breath and chanted:

I opened my eyes. The crystal had clouded over. Inside the ball, all the colours of the rainbow swirled together, and tiny red sparks spat out from its middle. One of them hit Aunty Wormella on the hand.

‘Ow!’ she squeaked.

‘Shhh!’ said Aunty Grizz.

‘Thanks for the sympathy,’ replied Aunty Wormella.

As I gazed into the ball, the colours cleared and a picture started to form. I could see a dark shape – a twitching shape with a long tail and whiskers …

‘There she is!’ I shouted. Charlie’s ears pricked up. He trotted to the kitchen table and stood against it on his hind legs. When he saw the tasty big rat, he dribbled all over the floor.

‘Go away, Charlie,’ I said. ‘She’s not dinner, so you can forget about that!’

I peered into the ball. Mrs Cuffy was crouched in a small room. She was squeaking quietly to herself and ripping a pile of blue cloth to shreds with her sharp little teeth.

I twiddled the knobs. The picture zoomed out, and I saw that the room looked familiar. Very, VERY familiar …

I zoomed out a little more. No wonder! It was my room! At this very moment, Mrs Cuffy was in my bedroom in our house, vandalising my wardrobe!

‘I don’t believe it!’ I said.

‘Where is she? What’s she doing?’ said Aunty Wormella, peering over my shoulder.

‘She’s upstairs!’ I said.

The two aunts leapt out of their seats and raced around the kitchen in a panic, bumping into each other and knocking things over.

‘Go and catch her, Grizz!’ shouted Aunty Wormella.

‘You catch her, Wormella!’ shouted Aunty Grizz.

‘Where are the traps!’ they both shouted at once, flinging open all the cupboard doors.

‘Shh,’ I said. ‘Look at that! She’s destroying my new jeans!’

‘Dear me, Anna,’ said Aunty Wormella, pausing. ‘If Mrs Cuffy disliked you when she was human, she seems to dislike you even more now she’s a rat!’

The aunts huddled behind me and we all stared at Mrs Cuffy’s furtive movements. She suddenly looked up from her destructive work, stared straight at me, and hissed.

I drew back from the crystal ball. The image went wavy.

‘You don’t think she can see me, do you?’ I whispered.

Aunty Grizz poked me sharply between the shoulder blades.

‘Zoom in again,’ she said. ‘You’re losing the picture.’

I sat forward and twiddled the knobs to zoom in. This time, behind Mrs Cuffy, I could see another dark shape moving slowly through the shadows of my room. What was that?

I twiddled the knobs again, but all I could see was a pair of golden eyes, unblinking, moving closer and closer to Mrs Cuffy …

Aunty Wormella glanced around the kitchen.

‘Oh dear. I don’t want to worry you, Anna,’ she said. ‘But where’s Charlie?’

I looked under the table. Charlie was nowhere to be seen. I swallowed hard and peered again at the dark shape with the golden eyes creeping through the darkness.

It was him, all right. He was upstairs trying to catch himself a late supper!

Mrs Cuffy suddenly stopped what she was doing. She twitched her ears and looked over her furry shoulder …

At that moment, the crystal ball went cloudy and the pictures disappeared with a loud ‘pop’.