Andrew McCarthy is best known as a movie star: a member of a group of glamorous young actors dubbed the Brat Pack, he starred in 1980s coming-of-age films such as St. Elmo’s Fire and Pretty in Pink, which helped define a generation. While McCarthy, 54, still acts and also directs, he’s branched out into writing in recent years. He has written for National Geographic Traveler and is the author of a travel memoir, The Longest Way Home (2012). Just Fly Away, his first published fiction, is a YA novel about 15-year-old Lucy, who discovers that her father has an eight-year-old son by another woman, and reacts by running off to Maine, where her paternal grandfather lives.

How has your background in film—acting and directing—influenced you as a writer?

From the directing point of view, it makes me focus on story, on the momentum of the story. You always try to tell what’s important to the story and what propels the story forward, what’s necessary, what’s not necessary. From the acting point of view, it keeps me focused on character and motivation—internal motivation.

When I write, I’m very much a visual person, a visual learner. As I write, I am visualizing [the plot]: I am playing the movie in my head.

You are a middle-aged man, whose previous experience is as a travel writer. How did you come to write a YA novel with a protagonist who is a teenage girl?

It doesn’t seem like a natural transition? I didn’t start out as a YA author. I was struggling for seven years on a novel about a marriage told in the third person, from the husband and father’s point of view. My favorite character in it was the 15-year- old daughter. One day I was sitting on a plane waiting to take off, and I just started writing from her point of view, in the first person. I started writing with the words, “My father is an asshole, he’s got another family living across town,” which was the story of the [original] novel. This guy had an affair and had this child that nobody in his family knew about. Suddenly, I started writing from the girl’s point of view and it liberated everything I’d been struggling with for years. I [already] knew all the characters, I knew where they lived, I knew everything about the family; but it was just an entirely different story, with this girl discovering her brother across town. And the story took off. So, I didn’t intend to, but this girl spoke up one day and I listened.

Was there a real-life inspiration in your life for this story line?

No, not at all. It’s the notion of secrecy that appealed to me, and then in families, how if, incrementally, you keep one little secret, then it grows and grows and grows. The two roads diverge by a tiny, infinitesimal bit in the beginning, and then they get wider and further apart.

What kind of research did you do into teen culture, including into the dynamics between teen girls?

The one thing I knew I didn’t want to have is a lot of phone device culture. I know it permeates teenage culture with all the texting. I was not interested in that. I don’t know it very well. I text occasionally, only because I have to. I wanted to create a scenario where her device was not part of the story. That was the largest hurdle. I spent a lot of time thinking about how I could get rid of her device. The rest was internal. I gave [the first draft] to my 15-year-old neighbor, a girl next door, and asked her to read it. She liked it and said, “It sounds just like my friends.” And I said, “OK, thank you.”

What is liberating about the YA world is I had no preconceptions about it, no baggage. It’s a thrilling time of life, really. Anything is possible. Everything is possible. And everything is important and has great magnitude. That’s great.

Are you concerned that scenes as Lucy smoking pot and being intimate with her boyfriend will arouse controversy among some parents and librarians?

It was just part of the story; it would be disingenuous of me not to mention [such subjects]. People experiment with drugs when they are teenagers and people experiment with sex when they are teenagers. It’s not like they are strong parts of the book. Avoiding it, to me, is not making it not so: it’s just sticking your head in the sand. After I wrote it, it did occur to me, whoa, is this going to be a big deal? [Lucy’s] limited experience with sex is a joyful experience for herbut it doesn’t dominate the story; it’s just a loving kind of moment. I don’t have an issue with that. People who doGod bless them.

Why did you choose the title, Just Fly Away?

It might refer to that moment in the book when these two misfits just want to escape. It’s hard; they just want to leave, they just want to fly away. Two people who are very alone fantasize about leaving, together. I guess that I experience that, being a travel writer. There’s something thrilling about leaving, just leaving. And I like the “just” part of it, because I like the minimizing of something of such magnitude. Teens tend to do that. And Lucy certainly tends to do that: minimize something that is very important.

Just Fly Away by Andrew McCarthy. Algonquin Young Readers, $17.95 Mar. 28 ISBN 978-1-61620-629-1