grew up in England,’ Gretchen said, hands wrapped round a steaming cup of coffee. ‘In the north Yorkshire countryside. I didn’t realise I could bookwander until I was an adult. I was working in a university library and I yanked Brutus out of Julius Caesar into the stacks with blood on his hands; I nearly had a heart attack. Thankfully one of the other librarians was a bookwanderer and realised what had happened and we had a day trip down to the Underlibrary, where I was offered an apprenticeship and then a job. I loved doing the most dangerous work I could find, and so I joined the research department, exploring unpredictable and out-of-print books, or books with multiple versions or strange histories. I loved it. You never knew what you would be doing or where you would be going from one day to the next.

‘After a few years I was paired up with Elsie, and we clicked immediately. Your grandma is a brilliant woman, Tilly, and the combination of my fearlessness and Elsie’s brain meant we made a great team and were given one of the Underlibrary’s most exciting projects: finding out more about fairy tales. But it was pitched to us as a project to help us understand them. Yes, to create some maps that meant bookwanderers could explore them more safely, but I didn’t realise that the bigger picture plan – which we hadn’t been told – was to try and work out why fairy tales behaved differently, with a view to forcing the usual rules on them. Elsie and I spent a good year exploring and mapping, and learning about the beautiful wildness of these stories, but, unbeknownst to us, everything we were learning was being analysed and used against the stories. When we found out, we protested, but were ignored. They wanted us to go into the stories to try and bind up some of the boundaries, to keep all the stories and characters in place. It was the final straw for me and I quit.’

‘But surely Grandma didn’t agree with all of that?’ Tilly said.

‘No, I don’t think she did,’ Gretchen said. ‘But she thought that the way to stop them was to work with them and convince them from inside.’

‘That sounds very sensible,’ Oskar said, earning him a hard stare from Gretchen.

‘It does!’ he maintained.

‘Well, Elsie did what she thought was right, and so did I,’ Gretchen said. ‘And I believe firmly that everyone should be free to follow their own path. I have no issues with the Underlibraries existing. I just don’t agree with their insistence on all bookwanderers registering with them and forcing them to be subject to their rules. I made my views clear, but I was happy to simply retreat, and yet that wasn’t good enough for the British Underlibrary. They insisted on withdrawing me.’

Clara gasped. ‘Gretchen! I did not know!’ she said, putting an affectionate hand on her arm.

‘What does that mean?’ Oskar asked.

‘Withdrawing is an antiquated process that bars someone from an Underlibrary,’ Gretchen said. ‘I am not permitted to enter the British Underlibrary as I am classed, ridiculously, as some kind of threat. I’m not sure if you are aware, but no one can take away your ability to bookwander, so it means very little, really, as I have no interest in ever going there again. It’s symbolic nonsense.’

‘I’ve heard some people talking about binding books to stop people bookwandering,’ Tilly said, choosing her words carefully so as not to give too much away, remembering Marcel’s warning about Gretchen. ‘What does that mean? Can they do that to you?’

‘Books aren’t interested in who is reading them,’ Gretchen said. ‘A book will welcome any reader; any age, any background, any point of view. Books don’t care if you can understand every word in them, or if you want to skip bits or reread bits. Books welcome everyone who wants to explore them, and thankfully no one has worked out a way to stop that. Of course, humans meddle, and at some point in bookwandering history, a bothersome librarian realised that books could be bound entirely, and that way you could stop anyone from bookwandering in them. They can still be read like normal books, but there’s no way to get inside.’

‘It is a barbaric idea,’ Clara said.

‘It’s not fair!’ Oskar said, outraged all over again at the thought.

‘It is what I have been trying to show you,’ Gretchen said. ‘The Underlibrary does not care about fair. It cares about power.’

‘That’s what Grandad said,’ Tilly remembered.

‘Well, I always thought he wasn’t so bad,’ Gretchen said. ‘When Elsie started going out with him, I did think she could have chosen a lot worse from among the ranks of librarians.’

‘Do bookwanderers often marry other bookwanderers?’ Tilly asked, curious.

‘Well, no, not always,’ Gretchen said. ‘But there is a reason bookwanderers often fall in love with each other. It is a big thing to share together – or not to share.’

‘What about falling in love with fictional characters?’ Tilly asked quietly, thinking of her mother.

‘Why, yes,’ Gretchen said, without a pause. ‘It would be madness to pretend that doesn’t happen. I have had several beautiful romances with fictional characters. I’ve been taken out for dinner by several iconic heroes and heroines in my time.’

‘But were you in love with them?’ Tilly pushed, knowing that her own mother had been head over heels for Captain Crewe inside A Little Princess. ‘Were you ever tempted to stay with them?’ Oskar shot her a warning glance.

‘I can’t say I was,’ Gretchen said. ‘I was too fond of my life here. But I believe people should be able to make their own decisions about such things. You have to make peace with either living inside a book forever or knowing you can’t really ever build a proper life with the fictional person you’re in love with. The Underlibrary is so hung up on just outlawing any romantic relationships – but how is it that different from the friendships we form with fictional characters, really?’

‘Yes, but I wouldn’t want to go and live in Anne of Green Gables forever,’ Tilly said. ‘However much I love being friends with Anne.’

‘And most people would agree with you,’ Gretchen said. ‘But don’t you think that people should be allowed to make up their own minds?’ She looked directly at Tilly. ‘And is it right to stop people if they aren’t causing any harm to anyone else?’

‘I … I’m not sure,’ Tilly said. ‘What if they were leaving behind people who needed them? Just hypothetically speaking.’

‘Well, I would say, hypothetically, that it is up to every person to decide what they are willing to sacrifice, and what is worth making sacrifices for. But whatever they decide, they should not be punished for it by a group of people who claim to have their best interests at heart, but are far more focused on trying to control bookwanderers.’

‘Do you think the Archivists would punish people?’ Tilly asked. ‘If they’re out there somewhere?’

‘I think the Archivists are there to help,’ Clara said. ‘They are not a literary police force.’

‘So you believe they are real?’ Tilly said.

‘Yes, I believe they exist,’ Clara said. ‘I think who they are, and what they are for, depends on what you are asking them. I think that they are perhaps buried in stories, hiding, or being hidden. Or just waiting for the right moment, peut-être. I would be disappointed after all this time to find they are no more real than these fairy tales.’ She smiled at Tilly but was distracted by a huge yawn from Oskar.

‘I think it’s time to get you two home,’ Gretchen said.

‘How is it only the afternoon?’ Oskar yawned. ‘I need a nap.’

‘You two are always welcome at the Faery Cabinet,’ Gretchen said as they wrapped themselves in coats and hats and scarves and headed back into the gentle snowfall. ‘And Tilly, I am assuming you will tell your grandparents about your adventure. Please remember we have all simply acted according to the principles we hold to be right and true in situations where there is no clear path.’ And with that she closed the shop door, and the three of them wandered home, Oskar arm in arm with Mamie.

‘Did you have a good morning?’ Gabriel asked as Tilly and Oskar wearily climbed the stairs and flung off their winter clothes.

‘Uh huh,’ Oskar murmured. ‘Very busy, need to sleep.’

‘I thought you just went to a bookshop?’ Gabriel said, looking confused. ‘Why on earth are you so tired?’

‘Maybe the fresh air?’ Tilly said, trying to be polite. ‘Or the travelling, bit of jet lag?’

‘I’m not sure you get jet lag from London,’ Gabriel said. ‘But I guess you’ve had busy days, and are still recovering from school finishing. You two have a nap, and I’ll bring you up some Orangina in an hour?’

‘Thanks, Dad,’ Oskar said, dragging his feet upstairs.

‘Merci,’ Tilly said. ‘I’m sorry.’

‘Nothing to apologise for,’ Gabriel said, watching them head upstairs with a perplexed look on his face. ‘Sleep well.’