‘How do we get back?’ said Yo-less.

‘It just sort of happens, I think.’

‘You’re just doing it with hallucinations, aren’t you,’ said Wobbler, never a boy to let go of hope. ‘It’s probably the smell from the trolley. We’ll come round in a minute and have a headache and it’ll all be all right.’

‘It just sort of happens?’ said Yo-less. He was using his careful voice again, the voice that said there was something nasty on his mind. ‘How do you get back?’

‘There’s a flash, and there you are,’ said Kirsty.

‘And you’re back where you left?’

‘Of course not. Only if you didn’t move. Otherwise you go back to wherever where you are now is going to be then.’

There was silence while they all worked this out.

‘You mean,’ said Bigmac, ‘that if you walk a couple of metres, you’ll be a couple of metres away from where you started when you get back?’

‘Yes.’

‘Even if there’s been something built there?’ said Yo-less.

‘Yes … no … I don’t know.’

‘So,’ said Yo-less, still speaking very slowly, ‘if there’s a lot of concrete, what happens?’

They all looked at Kirsty. She looked at Johnny.

‘I don’t know,’ he said. ‘Probably you kind of … get lumped together.’

‘Yuk,’ said Bigmac.

There was a wail from Wobbler. Sometimes, when it involved something horrible, his mind worked very fast.

‘I don’t want to end up with just my arms sticking out of a concrete wall!’

‘Oh, I don’t think it’d happen like that,’ said Yo-less.

Wobbler relaxed, but not much. ‘How would it happen, then?’ he said.

‘What I think would happen is, see, all the atoms in your body, right, and all the atoms in the wall would be trying to be in the same place at the same time and they’d all smash together suddenly and—’

‘And what?’ said Kirsty.

‘—and … er … bang, good night, Europe,’ said Yo-less. ‘You can’t argue with nuclear physics, sorry.’

‘My arms wouldn’t end up sticking out of a wall?’ said Wobbler, who hadn’t quite caught up.

‘No,’ said Yo-less.

‘Not a wall near here, anyway,’ said Bigmac, grinning.

‘Don’t wind him up,’ said Yo-less severely. ‘This is serious. It could happen to any of us. We dropped when we landed, right? Does that mean that if we suddenly go back now we’ll be sticking out of the floor of the mall, causing an instant atomic explosion?’

‘They make enough fuss when you drop a Coke can,’ said Johnny.

‘Where’s Wobbler gone?’ said Kirsty.

Wobbler was a disappearing shape, heading for the allotments. He shouted something.

‘What’d he say?’ she said.

‘He said “I’m off home!”’ said Johnny.

‘Yeah, but,’ said Bigmac, ‘… where he’s running now … if we’re where the mall is … will be … then over there’s the shopping estate. That field he’s running across.’ He squinted. ‘That’s where Currys is going to be.’

‘How will we know we’re about to go back?’ said Yo-less.