In Olsen’s debut, The Girl Before, self-deluded Clara Lawson must reevaluate her past after her husband, Glen, is arrested for human trafficking.

How do you make Clara, who’s both a victim and an unwitting abuser, a character readers can relate to?

We’re all willfully naive about certain aspects of our lives. I work as a therapist with a lot of low-income people. They see the world so differently than how I see the world. What if someone grew up thinking that the world worked a certain way? They could see evidence to the contrary, but at the same time, their beliefs are so strong.

How else did your background as a therapist affect the narrative?

No person is completely good or completely bad. Villains have a backstory. Glen didn’t start out being monstrous. He started out with hopes and dreams and through life and circumstances, and his desire to please his father and take care of Clara, he became someone different.

How do you account for the differences between Glen as a teenager and Glen as an adult?

He started out more one-dimensional —a stereotypical evil person. I thought of him as the abuser. But why did Clara feel devoted to him? What in their past would have lead her to have this strong connection with him?

How much of Glen’s family’s criminal enterprise had you mapped out in your own head?

I did a ton of research on human trafficking. The organization Clara is a part of is all made up, but the networks and the size of the trafficking industry is real. I actually downplayed it in the book. There are more slaves in the world today than there have been in all history. There are around 27 million to 30 million slaves in this world today, with over 30,000 in the United States. There are slave ports in all 50 states. It’s a very large industry that somehow has stayed very hidden.

When Clara first came alive to you, was it the naive version at the beginning, or the more self-aware version at the end?

Somewhere in between. Despite her naïveté, she’s a very strong individual, for everything she has to go through, to protect the girls, to protect Glen.

How did you decide on the structure, which alternates between past and present?

That’s how it came to me. The opening scene was the first I ever wrote. Clara is remembering her past, and the past and present scenes eventually connect. It made it more of a puzzle—for me too, as I was writing it. Why would she be thinking this or doing this? It became clear as her past clicked into place.