‘And bend and bend and bend and – do the best you can, Miss Windex – step and step and – what?’

She blinked.

Johnny looked around.

The keep-fit class, after ten minutes of aerobics, were not the most observant people. One or two of them actually made space for the newcomers.

The tutor hesitated. She’d been brought up to believe in a healthy mind in a healthy body, and, since she was pretty sure she had a healthy body, it was not possible, she reasoned, that a group of people and an overloaded shopping trolley could have suddenly appeared at the back of the old church hall. They must have just come in, she reasoned. Admittedly, there was no actual door there, but people certainly didn’t just appear out of thin air.

‘Where are we?’ Kirsty hissed.

‘Same place,’ whispered Yo-less. ‘Different time!’

Even some of the slower fitness fans had caught up by now. The whole class had stopped and turned around and were watching them with interest.

‘Well, say something!’ said Kirsty. ‘Everyone’s looking.’

‘Er … is this Pottery?’ said Johnny.

‘What?’ said the tutor.

‘We’re looking for Beginners’ Pottery,’ said Johnny. It was a wild stab, but every hall and hut and spare room in Blackbury seemed to have its time filled up with people doing weird hobbies or industriously learning Russian.

A small light went on behind the tutor’s eyes. She grabbed at the familiar words like a singer snatching a microphone.

‘That’s Thursdays,’ she said. ‘In the Red Cross Hall.’

‘Oh. Is it? Tch. We’re always getting it wrong,’ said Johnny.

‘And after we’ve lugged all this clay up here, too,’ said Yo-less. ‘That’s a nuisance, isn’t it, Bigmac?’

‘Don’t look at me,’ said Bigmac. ‘They shot at me!’

The tutor was staring from one to the other.

‘Er. Yes. Well, it can get pretty nasty in Beginners’ Pottery,’ said Johnny. ‘Come on, everyone.’

They all grabbed hold of the trolley. Tracksuited figures limped politely out of the way as it squeaked its way across the floor, bumped down the step and landed in the damp yard outside.

Johnny pushed the door shut behind them, and listened for a moment.

‘… well, then … bend and stretch and wheeze and bend …’

He straightened up. It was amazing what you could get away with. Ten-legged aliens would be immediately accepted in Blackbury if they were bright enough to ask the way to the Post Office and complain about the weather. People had a way of just not seeing anything that common sense said they shouldn’t see.

‘I bet something’s gone wrong,’ said Bigmac.

‘Er …’ said Yo-less.

‘No, this has got to be the 1990s,’ said Kirsty. ‘It’s the only period in history when you wouldn’t be burned at the stake for wearing a green and purple tracksuit, isn’t it?’

The bulk of the sports centre loomed opposite them. Five minutes ago, thought Johnny, five of my minutes ago, that was a street. Get your head round that.