‘You’ll have to leave from this exact spot when you go to get her,’ she explains. ‘Different places on the Earth’s surface relate to different parallel universes. I once tried to return to a universe I’d already been to, but I was careless and didn’t keep track of exactly where I left from the first time. So it didn’t work and I ended up somewhere completely different.’

‘Oh.’ My insides curl. What if I haven’t remembered exactly where Mum was standing when she disappeared?

‘Usually, I didn’t care where I ended up,’ she says. ‘There were always opportunities of some sort or another wherever I landed.’

‘Opportunities? You didn’t go for a disappearing act?’

‘No.’

‘Hang on!’ I say. ‘Who was the person to go and get you if something went wrong?’

‘Your mother, of course,’ Sylvie says smoothly.

What?! But of course. Why didn’t I realise this before? ‘How often did she go?’ What I don’t ask – because I know very well that she’ll snap at me – is whether that was when Mum encountered the terrible danger Vince and Dad have mentioned.

‘She went a fair few times,’ says Sylvie vaguely. ‘I’d pop over and see what opportunities there were, and she’d fetch me a couple of days later. Once I landed in an American town and spotted the version of me that lives there, and she looked super sporty, like a … I don’t know, a personal trainer or something.’ She laughs. ‘Who knows at what point my life branched off and led me there.’

My heart gives a stutter. ‘Wait! You met another version of yourself? Does that mean there’s another version of Mum over there, where I’m going?’

‘You didn’t realise that? It’s a parallel universe, Tulsi. Not a totally different planet. Much of what’s in this universe is likely to exist there, too. Including your mother. Or a version of her, anyway.’

What? Two mums? My brain is not computing that. TWO MUMS? You’ve never actually mentioned that, Sylvie! I think.

‘So when I get there,’ I say, ‘there will be Mum and … another Mum?’

She nods, as if that’s no big deal.

‘And will there be another me?’ I ask, feeling suddenly dizzy.

‘Maybe. The parallel Tulsi might be living a very similar life in that universe. Or you might not exist at all. It would depend on whether the Merry in that universe ever met the Dave in that universe, and whether they had you.’

‘Oh.’ I’m struggling to make sense of all this.

‘I tried to avoid the other versions of me. I once ran into one in a shop and she knew who I was, of course, and we told the shop owner we were twins.’ Sylvie smiles. ‘I was the more glamorous twin, naturally.’