Hugo shrugged. ‘If I was religious, I’d say it was God. And as God is probably someone we can’t see or comprehend then He – or She – or whichever pronoun God is – becomes an image of someone good we have known in our lives. And if I wasn’t religious – which I’m not – I would think that the human brain can’t handle the complexity of an open quantum wave function and so it organises or translates this complexity into something it understands. A librarian in a library. A friendly uncle in a video store. Et cetera.’

Nora had read about multiverses and knew a bit about Gestalt psychology. About how human brains take complex information about the world and simplify it, so that when a human looks at a tree it translates the intricately complex mass of leaves and branches into this thing called ‘tree’. To be a human was to continually dumb the world down into an understandable story that keeps things simple.

She knew that everything humans see is a simplification. A human sees the world in three dimensions. That is a simplification. Humans are fundamentally limited, generalising creatures, living on auto-pilot, who straighten out curved streets in their minds, which explains why they get lost all the time.

‘It’s like how humans never see the second hand of a clock mid-tick,’ said Nora.

‘What?’

She saw that Hugo’s watch was of the analogue variety. ‘Try it. You just can’t. Minds can’t see what they can’t handle.’

Hugo nodded, as he observed his own watch.

‘So,’ Nora said, ‘whatever exists between universes is most likely not a library, but that is the easiest way for me to understand it. That would be my hypothesis. I see a simplified version of the truth. The librarian is just a kind of mental metaphor. The whole thing is.’

‘Isn’t it fascinating?’ said Hugo.

Nora sighed. ‘In the last life I spoke to my dead dad.’

Hugo opened a jar of coffee and scooped out granules into two mugs.

‘And I didn’t drink coffee. I drank peppermint tea.’

‘That sounds terrible.’

‘It was bearable.’

‘Another thing that is strange,’ Hugo said. ‘At any point in this conversation you or I could disappear.’

‘Have you seen that happen?’ Nora took the mug Hugo handed her.

‘Yeah. A few times. It’s freaky. But no one else would notice. They become a bit vague with their memory for the last day, but you would be surprised. If you went back to the library right now, and I was still standing here talking to you in the kitchen, you would say something like “My mind’s just gone blank – what were we talking about?”, and then I’d realise what had happened and I’d say we were talking about glaciers and you’d bombard me with facts about them. And your brain would fill in the gaps and make up a narrative about what just happened.’

‘Yeah, but what about the polar bear? What about the meal tonight? Would I – this other me – would she remember what I ate?’

‘Not necessarily. But I have seen it happen. It’s amazing what the brain can fill in. And what it is fine with forgetting.’

‘So, what was I like? Yesterday, I mean.’

He locked eyes. They were pretty eyes. Nora momentarily felt pulled into his orbit like a satellite to Earth.

‘Exquisite, charming, intelligent, beautiful. Much like now.’

She laughed it off. ‘Stop being so French.’

Awkward pause.

‘How many lives have you had?’ she said eventually. ‘How many have you experienced?’

‘Too many. Nearing three hundred.’

‘Three hundred?’

‘I have been so many things. On every continent on Earth. And yet I have never found the life for me. I am resigned to being this way for ever. There will never be a life that I truly want to live for ever. I get too curious. I get too much of a yearning to live another way. And you don’t need to make that face. It’s not sad. I am happily in limbo.’

‘But what if one day there is no video store?’ Nora thought about Mrs Elm, panicking at the computer, and the flickering lights in the library. ‘What if one day you disappear for good? Before you have found a life to settle in?’

He shrugged. ‘Then I will die. And it means I would have died anyway. In the life I lived before. I kind of like being a slider. I like imperfection. I like keeping death as an option. I like never having to settle.’

‘I think my situation is different. I think my death is more imminent. If I don’t find a life to live in pretty soon, I think I’ll be gone for good.’

She explained the problem she’d had last time, with transferring back.

‘Oh. Yeah, well, that might be bad. But it might not be. You do realise there are infinite possibilities here? I mean, the multiverse isn’t about just some universes. It’s not about a handful of universes. It’s not even about a lot of universes. It’s not about a million or a billion or a trillion universes. It’s about an infinite number of universes. Even with you in them. You could be you in any version of the world, however unlikely that world would be. You are only limited by your imagination. You can be very creative with the regrets you want to undo. I once undid a regret about not doing something I’d contemplated as a teenager – doing aerospace engineering and becoming an astronaut – and so in one life I became an astronaut. I haven’t been to space. But I became someone who had been there, for a little while. The thing you have to remember is that this is an opportunity and it is rare and we can undo any mistake we made, live any life we want. Any life. Dream big . . . You can be anything you want to be. Because in one life, you are.’