When gardening writer Amy Stewart was researching The Drunken Botanist (Algonquin, 2013), about the intersection of botany and booze, she came across Henry Kaufman, a gin smuggler from a hundred years ago. Although she hasn't been able to verify that he's the same Kaufman who ran a silk-dyeing factory in Paterson, N.J., and got into an "over-the-top" dispute with three sisters—Constance, Norma, and Fleurette Kopp—after his car hit their horse-drawn carriage, Stewart was hooked. She even switched genres to historical fiction to tell the story in the voice of Constance in Girl Waits with Gun (Houghton Mifflin Harcourt, Sept.).

As the title, which is taken from a newspaper headline of the time, indicates, Stewart hasn't forsaken research to make her fiction debut. "I spent the first year or two doing nothing but research. That was all familiar territory to me," Stewart says. "I started with a New York Times article and used genealogical records going all the way back to Germany. I'm very big on going back to primary sources."

Part of the reason for the genre shift was that the historical records weren't complete, and to make a more compelling story she needed to be able to take liberties. "My ambition was to take what really happened and use fiction to fill in the gaps," she says. "I tried to find a way to let Constance's world come to life. I've been to Paterson and to Hackensack. I stood on the corner where the girl waited with the gun. But I allowed Paterson and Hackensack to change a little bit. At some point, I had to let go of the real characters and the real place." She added a post script so that readers can separate fact from fiction.

Stewart readily acknowledges that the Kopp sisters have taken over her life. While she was writing Girl Waits with Gun, she worked on a series of watercolors—she's been painting for the past decade—of gangsters from that era using real mug shots. Her reading is now largely fiction from the early 1900s, along with court records and newspaper clippings. "I don't think I'm going to stumble on anything like this again. These women grabbed me," says Stewart, who is already at work on a sequel.

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