In 1998, beloved British children’s author Eva Ibbotson released The Secret of Platform 13, offering readers a glimpse into a fantastical world with myriad magical creatures, a case of mistaken identity, and a King’s Cross portal to a special island. Ibbotson died in 2010, but now readers can revisit the Island of Mist in Beyond Platform 13, a sequel set years later, imagined by Sibéal Pounder, author of the bestselling Witch Wars and Bad Mermaid series. Pounder spoke with PW about the process of writing a sequel to someone else’s work, the impact of research on this novel, and what readers can expect from her next.

How did you first encounter The Secret of Platform 13? What made you decide to write a sequel, and how did you come up with the character of Lina?

I was around nine years old. I loved Eva Ibbotson’s books, and I loved The Secret of Platform 13 most of all—especially the young hag Odge Gribble. When Eva’s estate and publisher approached me about writing a sequel, it was very surreal. I was so excited to venture back into a world that I had loved so much as a child. The character of Lina in many ways represents all of us who met The Secret of Platform 13 characters when we were younger and longed for them to be real. As the sequel takes place nine years later, and many of the child characters are now teenagers, Lina allows for that direct link to the readership. I also wanted her to represent the unswerving belief in magic that you have when you’re younger, and juxtapose that against an older Odge, who now sees the world a little differently.

Can you talk about the process of writing a sequel to someone else’s story?

I really wanted to be respectful of the world Eva created, and I wanted to take the story and the characters in a direction she would be happy with. She sadly passed away in 2010 so I couldn’t ask her, but her children looked over all the plans. I also spent months researching to try to find any hints as to where she would have taken the story or characters. One big clue is in the book itself—very early on, she states that every country in the world has a gump, a secret portal, which allowed me to take the story from London to Vienna.

In terms of characters, I looked for clues as to how she might have crafted them in future books by working backwards and figuring out who they might be based on. For example, Ben, the prince in the first book, was interesting to me, and I considered possibly corrupting him in the sequel. But I noticed the language she used to describe Ben was almost identical to the language she used to describe her beloved husband. I then found an old article detailing how she first met her husband, and she says he cared very much about creatures—so much so, he made a little ant farm and kept it hidden under his bed. In The Secret of Platform 13, Ben makes a den for a mistmaker creature and keeps it hidden under his bed. I felt confident then that she would never corrupt Ben—so that helped guide me in building his story going forward.

You’ve also written your own successful series. How was this latest project different from, or similar to, writing your own sequels?

It was very different because I felt a responsibility to create something that was in line with where Eva would take the story. I wanted to feel confident that I could explain every decision in the book, and that every decision led back to Eva. It was a really fun and interesting way of working, and I loved meeting her children, who are just as magical as the characters in her books. I very much skipped into the first draft like an excited child let loose in one of her all-time favorite fictional worlds!

What’s up next for you? Do you have any plans to write sequels for other books?

No plans at the moment to write any more sequels to other books—the Eva project was a very special one-off. I’m currently working on a Christmas book, called Tinsel, which is all about the character we have come to know as Mrs. Claus. It asks the question: what if somewhere along the way we’ve all got the Santa story a bit wrong? Definitely not a sequel—more of a prequel.

Beyond Platform 13 by Sibéal Pounder, inspired by Eva Ibbotson. Viking, $16.99 Feb. 2 ISBN 978-0-593-20417-7