Sitting with Phillip Margolin in Portland, Ore.’s legendary Bread and Ink Cafe, I ask him about his upcoming novel, Worthy Brown's Daughter (Harper, Feb). Set in 1860s Oregon, the story centers on the titular Worthy Brown, a freed slave whose daughter is being kept illegally as a slave by Caleb Barbour, a shady, cruel lawyer.

Margolin is best known for his contemporary legal thrillers—most recently, Sleight of Hand (Harper, Apr. 2013), but in Worthy, he turns back the clock. Margolin, a former criminal defense attorney, stumbled upon the idea for this novel when he read about Robin Holmes v. Nathaniel Ford, a 1853 case in the Oregon Territory. “It was a really sad case,” Margolin says. “Col. Nathaniel Ford brought a family of slaves to the territory from Missouri—two parents and their children—with the promise that if they helped him set up a farm in Oregon, where slavery was illegal, he’d free them.” Ford reneged on his promise, freeing only the parents and a newborn, and keeping the remaining four children as slaves.

Portland, and Oregon in general, wasn’t always the beacon of liberalism it is today, and the Ford case, as well as Margolin’s fictionalized version, brings the city’s more conservative past into sharp relief. “Oregon was very racist at the time. The Oregon Constitution says that no free negro not living in Oregon when the constitution was passed could live in Oregon, own property, or make contracts,” Margolin says, rattling off legal citations with the ease of an attorney. “It was an exclusionary rule, and so these two illiterate ex-slaves [in the Ford case] had to find a white lawyer to represent them. They did, and the chief justice of the Oregon Supreme Court finally ruled that Ford couldn’t keep the children as slaves, but by that point, one of them had died. It was heartbreaking—and I thought that it would make a great novel, so I just started researching.” Margolin notes, “Writing is the easy part for me—just sitting down and writing. But coming up with an idea to fill up a 400-page book? That’s really hard.”

The research for Worthy Brown's Daughter would take years, and the drafting phase even longer. Margolin read many of the great Russian novels during the early years of working on Worthy, “so I thought that if I’m writing a serious novel, everyone either has to be miserable or dead by the end of the book.” But the final book, Margolin says, which took him more than 30 years, is completely different from the many early versions. “At one point, there were two main characters: one who commits suicide and the other who has lost his wife and falls in love again, but is so depressed that he gives up the woman he loves and wanders aimlessly through America.”

While the new novel might seem like a thematic departure for him—going from contemporary courtroom whodunits to a historical novel about race relations in 19th-century Oregon—Margolin prefers to think of it simply as a long-gestating idea that needed a “bigger” book than he originally envisioned. “People often ask me if I’d like to write in a different genre,” he says. “And I say, ‘Sure, if I get an idea, I’d love to do it.’ ”

Margolin has used real events for the basis of a book before. His first novel, 1978’s Edgar-finalist Hearthstone (Harper), is a fictionalized account of one of Portland’s most famous murder cases: the 1960 double homicide of 19-year-old lovers Beverly Allan and Larry Peyton in Forest Park. That was one of his “big” books, and he says he wasn’t even thinking, “I’m going to write a murder mystery,” but rather, “I am going to write a novel.” Hearthstone takes place over 20 years and has a huge cast of characters. His second book, he says, was much smaller. “It’s all about the idea for me. Sometimes they’re big ones, sometimes they’re small.”

Margolin recently participated in the International Thriller Writers (ITW) USO Tour. Along with fellow mystery authors Harlen Coben, F. Paul Wilson, and Heather Graham, and ITW board emeritus Kathleen Antrim, he traveled to Washington, D.C., met recovering soldiers at Fort Belvoir, and visited Walter Reed Hospital. The details of the trip were not released until after the authors returned, so I had to wait to hear the particulars until a few weeks after our meeting. “The next day we went to Quantico,” Margolin says, which sounds like the beginning of one of his thrillers. “We flew to Kuwait where we visited two Army bases. From Kuwait, we went to Rahmstein, Germany, and on to more hospitals to visit with wounded soldiers.” The authors brought copies of their books to give out at each hospital and base. When I ask Margolin about his favorite moment from the trip, he says, “Meeting with a seriously wounded soldier in the hospital in Germany. We had heard that he was looking forward to our visit because he wanted to be a writer. The look on his face when I introduced myself made the trip worthwhile. He was so excited to talk about novel writing, outlines, editing, etc. I would definitely make this trip again.”

As for the new book, Margolin hopes that Worthy Brown's Daughter will attract fans who might not normally read his work (“You’d have to be pretty egotistical to think that everyone will like all of your books, it’s not like I like everyone else’s books!”) —especially those whose tastes skew more toward literary and historical fiction.

When Worthy Brown's Daughter comes out in February, Margolin will make appearances at the Oregon Historical Society and the Friends of History at Portland State University, along with fellow author Greg Nokes, whose book, Breaking Chains: Slavery on Trial in the Oregon Territory (Oregon State Univ., 2013), Margolin recommends to anyone interested in learning more about one of the bleaker periods in Oregon’s history. Worthy Brown’s Daughter brings that history to life.