In Caroline Woods’s The Mesmerist (Doubleday, Sept.), three women in a Minneapolis home for unwed mothers join forces to take down a serial killer.

The novel pulls from two historical sources: the women living and working in Bethany Home for Unwed Mothers, and the murders committed by socialite Harry Hayward. What led you to combine them?

I live in the Midwest, so I was looking for inspiration in historical stories that took place near home. I was intrigued by the progressive women of the time, like Jane Addams in Chicago, and that led me to Bethany. I was struck by the modernity of the women who ran it. They recognized the need for universal childcare, job training, and support for immigrant women. I brought the idea to my editor, and she said, “The Bethany Home is ripe for a story. But where’s the conflict?” Then I read some general history of Minnesota in the 19th century, and I came across Hayward. If he really was a serial killer, and we’re meant to believe his jailhouse confessions, he would have started before the more notorious Chicago murderer H.H. Holmes.

How did you select which real-life women to focus on?

Abby Mendenhall was one of the founding members of Bethany, and she was at the home the most. I read something she wrote on her 37th birthday—“Another monotonous year has passed. Shouldn’t marriage be what all women aspire to?”—that gave me the sense she was growing bored with her life. She wanted to give her life meaning, and this investigation is how I let her do that.

How important was it for you to depict the Gilded Age in a fresh way?

I was interested in getting out of the manor house and out of the East Coast. There was so much else happening all across the country. The theme of income inequality is always on the edges of these stories, but I wanted to look at how people were living who weren’t working in the big houses.

Why did you decide to make mesmerism part of the narrative?

It was a necessary piece. There was a rumor about the killer, that he was a mesmerist. It used to be a totally acceptable criminal defense to claim you were mesmerized to kill and you got a lighter sentence. That was how strong the belief was in that kind of thing in the post–Civil War era. One possible explanation for the belief was the invention of the telephone and the telegraph. If these invisible forms of communication were possible, then people were willing to accept mind control. One of the most uncanny things I came across in my research was that Harry Hayward hired a medium, a young woman, to convince his future victim that it was okay to trust him. When I read that, I thought, “Oh, that’s how I can tie him to the women who went into the Bethany Home.”