Margaret Peterson Haddix published her first novel for young readers, Running Out of Time, in 1996 and has since published more than 41 books. In her new series, which begins with The Strangers, three siblings—Chess, Emma, and Finn Greystone—investigate their mother’s disappearance and learn of an alternate world while cracking codes, solving clues, and uncovering secrets. Haddix spoke with PW about the seed of an idea planted more than 30 years ago, the appeal of writing a cast of siblings, and her transition from journalist to novelist.

From where did the inspiration for this unique series premise come?

Out of all the books and series I’ve ever written, this is definitely the one that had the longest gestation period. The original seed was planted by a newspaper column I read 31 years ago. It was about a weird circumstance: a mother of three small children happened to read about a car accident [that caused] the tragic deaths of three other children. The three children who had died were the same ages as her kids. The oldest two had the same names as her oldest two children and the third child had the name they would have used if the child had been born a boy. For a period of time, she was too terrified to drive her own car because of the eerie coincidences. The story stuck in my mind because it was so weird.

A couple years ago, I started thinking about the potential of the story in the column. I considered what it would be like to be aware of all those similarities as one of the surviving kids. And then I thought, that’s interesting, but what if those other children didn’t die? What if they were kidnapped? Then there’s still some chance of rescue.

Did you know from the start that it would be a story told in multiple volumes?

I was pretty sure from the beginning that it would be a series. There was a lot I didn’t have figured out—there was no bolt of lightning. I still don’t know everything and I’m about 50 pages into writing the third one now.

Do you plot and plan your novels or do you tend toward a less structured writing process?

I’ve done both approaches. I’ve settled into having a very broad overarching plan, but the specifics remain pretty vague. My plans change a lot as I’m writing.

What was your process for coming up with codes, clues, and mysteries that the siblings encounter throughout the novel?

As I was thinking about this story, I realized there would have to be a fair amount of secrecy involved. And, to have that level of secrecy, you need to have some way of keeping those secrets. Some of the codes in the books have a historical basis, but some I made up based on things unique to the characters in the book.

Creating the codes and clues was a lot of fun for me. I did a fair amount of research into the history of codes and read many books for kids about secret codes. I also went to the cryptologic museum, which is in Maryland, right beside the NSA.

Your books are suspenseful and fast-paced. Do you have a method for maintaining suspense throughout a novel or series?

I don’t know that I would call it a method. [laughs] I’m always thinking about what made me stop reading or skip sections as a kid. I remember about how much I loved cliffhangers. Those things are important to tap into when writing.

Is writing from the perspective of tight-knit siblings a different experience than unrelated individuals? How do you approach developing familial relationships?

Part of the reason I like to write from sibling perspectives is because I’m one of four kids. My brothers and sister and I were very close growing up. To a certain extent, when we wanted to play with someone it had to be a sibling because there weren’t a lot of kids around, but we also enjoyed being together. My own kids are very close in age and have overlapping groups of friends. Writing sibling relationships feels very natural to me.

There’s also a lot to be said for writing a group of kids where it’s siblings because there is more opportunity to have differences in personalities and interests and still have a reason for those kids to have to hang out together.

How did you get your start in publishing? What prompted your jump from journalism to fiction?

I had always wanted to write fiction. When I went to college, I studied both creative writing and journalism. I thought creative writing wasn’t the most practical major, so journalism would allow me to write and earn a paycheck. It felt more sustainable. I also majored in history because I enjoyed the subject; I didn’t think it had a practical use, I just threw it on for fun. It’s funny how it worked out. I’ve written historical and time travel novels, so it ended up being more practical than I anticipated.

Even when I was writing as a newspaper reporter, I was writing a lot of fiction on the side. My first three books were all inspired by something that I covered as a reporter. It worked very well to make that transition. It was very good training.

Did you know that you wanted to write for young readers?

I didn’t. I was throwing things at the wall to see what would stick. That was my approach. [laughs] I was writing all types of fiction, but, when I got the idea for my first book, Running Out of Time, I felt pretty strongly that it needed to be a book for kids. Then the idea for my second book was a teen book.

I didn’t have it all figured out at the beginning, but, looking back, it really makes sense that I’m writing for kids. When I was 10, books were so important to me. Reading played such a huge role in my life.

How did you eventually break into the publishing industry?

It was the early ’90s and the advice people were giving was mixed. Some said I didn’t need an agent to write for children and others insisted I did, so I tried both approaches. Ultimately, I ended up at a writers’ conference and an agent from McIntosh & Otis passed my manuscript along to Renee Cho, who was at the same agency. She became my first agent.

You’ve had more than one agent?

Yes, Renee eventually left agenting. I stayed with the same agency and Tracy Adams became my second agent. Eventually, Tracy left McIntosh & Otis to form her own agency. I stayed on as Tracy’s client.

Do you feel that, over the course of your career, the industry has changed in ways that affect your approach to writing for young readers?

I'm not sure that the writing itself has changed, but the career has definitely changed. The internet and social media have changed things. When I was starting out, I felt like, for the most part, the job was just to write the book. Now there’s so much emphasis on communicating with readers online and in-person, which is in many ways wonderful, but it’s also really hard to find balance.

I'm constantly reevaluating what my right balance is. I tend to go into writer cave mode when I’m really deep in a manuscript. I ignore everything else. It’s good for finishing the book, but, when I’m finally out of that mode, I have so many messages that need responses.

Do you often have the opportunity to meet readers?

I do! I know authors who do 100 visits a year, but I’d ideally like to limit my visits to 25–30 visits per year. I actually went back and counted how many school and library visits I did last year: 44. Some were half days, some full, some a day and a half, so it’s a variety of time commitments.

What advice would you give to a writer who is just entering the industry?

It’s hard to say because I feel like I had to learn from the mistakes I made. And a lot has changed since! I look at people who are starting out now and am so impressed. The debut authors today are so savvy about social media and are much better public speakers than I was when I was starting out. So many of them hit the ground running, so I hesitate to give advice!

I think, in general, I wish I had been less stressed and worried. I suppose it made me more conscientious. Maybe I needed that.

What’s in store for readers as this series progresses? Are you working on anything else?

There are still lots of unanswered questions at the end of this first book, but there are many more answers in the second book!

I also have a standalone middle grade book coming out in September called The Remarkables. It’s totally unrelated to the series and is a bit of a departure from what I normally do.

The Strangers (Greystone Secrets #1) by Margaret Peterson Haddix. HarperCollins/Tegen, $17.99 Apr. 2 ISBN 978-0-0628-3837-7