Jack, the five-year-old narrator of Emma Donoghue's Room knows only the world inside the 120-square-foot soundproof cell he and his mother have been imprisoned in for years.

Several news stories recently concerned a woman and a child held in captivity. Was there one that inspired you to write Room?

The idea came to me a few days after reading about the case in Austria. That was very unusual. I've never before been so blessed by an idea for a novel. Yet my book is not close to that case at all. In none of the real-life cases was the kidnapper such a sinister controlling figure in the lives of his captives.

How old were your own children when you started writing the book?

My kids were four and eight. I think that many years of parenting had been preparing me mentally. I knew the story had to be told by Jack. I would have had no interest in telling it from the mother's point of view. That would have been a true crime story or a sob story, and I didn't want that at all.

How did you decide on the dimensions and furnishings of the room?

I wanted to give my characters the minimum state in which they could survive. I didn't want their conditions to include malnutrition or bad ventilation. I wanted the mother to be able to keep the space safe and clean. I wanted people to believe in Jack and Ma and every inch of that room.

How did you come up with the homemade toys, learning games, and exercises that Jack's mother invents?

I had some ideas starting out, but others just occurred to me as I wrote. Any parent knows how to be the ideal parent. We start out by playing a game with our kids, but then we become impatient or lose our tempers. So the biggest challenge was to get the balance right. I didn't want Jack's mother to be too saintly. On the other hand, I wanted their relationship to be one of ongoing closeness and comfort.

Was it difficult to create the escape plan?

I asked my son [who was then six] to let me see how difficult it would be to get out of a rolled-up rug. He literally lay down and tried, and I watched and wrote about it. I also made a study of his language. I drew up kind of a short list of verbal mistakes that were amusing and also revealed how a child thinks.

Was it always your intention to write about the captivity followed by sudden freedom, or did the second half of your story develop as you wrote?

I always knew that it was going to be a story in two halves. I didn't want people to think: they're out; now there will be a happy ending, like Alice in Wonderland. I wanted Jack to discover himself as independent from his mother. And I wanted her to have all those moments when she longed for some separation from him.

Do you think this is a novel that only a mother could have written?

Not necessarily. Other people have written well about the parent-child relationship. We Need to Talk About Kevin is one of the best books I've ever read about that situation. Though it's a dark portrait, it made my task a lot easier.