I sit right here at this sofa and write on my laptop. It's quiet. I write about two hours a day, and I write in fits and spurts — 45 minutes here, a half-hour there — and when I get stuck, which happens often, I take the dogs for a walk. But during the time when I'm not actually writing, I'm thinking.

You've said you start with characters, not plots. What do you mean?

I try to get to know my characters really well before I write. Where I start is to ask myself what my characters really, really want. What is their heart's desire? In life, everything you do, you do because there's something you want — something big or small, physical or emotional. Characters are like that. You try to make it difficult for them to get what they want, but their desire is … the engine that drives the car forward.

From that point on, I become like a stalker. [Laughs.] I stand right behind my characters and watch where they go. I manipulate them some, but if I try to micromanage too much, that's when I tend to get [writer's] block.

As a reader, what did you like so much about "The Secret Garden"?

I loved reading a book where the main character was really just unpleasant. Mary is described as this sullen, nasty, tough, very unattractive little girl. But she was smart. That's rare. I loved it!

On another level, I loved the way reality and magic melt together in the book. I'm sure that has had some influence on me. That element is there in all of my books. For instance, there's a ghost in every one. I don't make a fuss about it. They just come in and out.

How did the Humming Room project happen?

My editor, Jean Feiwell, came to me with the idea. As it happens, I had a copy that was completely dog-eared. I actually re-read "The Secret Garden" every year. But when I sat down to work on it, I realized I'd gotten myself into a mess. This was the scariest book I've written.

What were the biggest challenges?

For one thing, there's a secret in the book, but everyone [who has read it] knows what the secret is. How do you write about a secret when everyone knows what it is? That was tricky.

I also wanted to follow the story line pretty closely — it's a great story line — but also retell the story in a fresh, surprising way. If you don't do that, why bother?

How'd you approach the project?

I knew I had to make the setting different [from the English moors]. I was toying with all kinds of ideas. I initially thought of New York City — that would be interesting, to have the secret garden be in an urban environment. But the main character has to be isolated, so that wouldn't work.

At the time we were living in this lovely, tiny little town, Clayton, N.Y., right on the St. Lawrence River. I'd sit there on the pier to do my writing. And one day I found myself looking at this gorgeous river and these islands — the Thousand Islands — which are covered by these vast mansions built by millionaires early last century. There are creepy stories attached to all these places. I thought, "You're an idiot. It's right here!"

In the book, she lives in a house had been a tuberculosis hospital. Is there really such a place?

Not in New York. I was looking online, though, and learned about this old sanitarium that had what they called a body chute. These places were awful at helping people. They'd have patients walk outside in the freezing cold because they thought it was better for their lungs, stuff like that. … And they used these chutes to dispose of bodies [to avoid bad publicity]. I thought: That's one way to create secrets that weren't in the original.

How about the main character?

Roo popped right out. She was very easy to write. She feels like a half-savage in the beginning. She's so wild, raw and shut in, just like the garden. She's a person who's interested in things, but she's in survival mode. I think that makes readers root for her.

Do you counsel young writers?