Sadeqa Johnson has always written stories about subjects she knows well, but the story of Yellow Wife called to her on a different level — one she was not familiar with.

“Yellow Wife was a complete surprise for me,” she said. “My first three novels are all contemporary fiction, and steeped in subjects that I knew pretty well. Like my first novel, Love in a Carry-On Bag, is a long-distance love story and I started off in a long-distance love story with my husband. Yellow Wife actually kind of found me, so to speak.”

A year after Ms. Johnson moved to Richmond, Va., she walked the Richmond Slave Trail with family and friends. There she discovered the story of Mary Lumpkin, an enslaved woman married to Robert Lumpkin, owner of Lumpkin’s jail and nicknamed the bully trader.

“I just became enamored with the little bit of her story that I got just from the marker that was on the actual slave trail,” Ms. Johnson said. “And I think what caught my attention was that they were married, and so first I’m like, that’s not even possible because we’re talking about the 1800s, when blacks and whites couldn’t marry.”

The more she thought about Ms. Lumpkin’s story the more she wondered about her life married to the jail owner.

“The jail was described as one of the most horrific places on Earth,” she said. “It was a slave pen, it was a punishing center. In fact, nearby planters, when they wanted to make an example of their slave, they would send that person to Robert Lumpkin for punishment. And that was the draw for me to the story. I was just curious about her life.”

Ms. Johnson said that when she and her family traveled further up the slave trail and visited the sacred African Burial Ground, she felt a calling.

“The energy that we felt was so strong. It’s like the trees are... trying to communicate, they’re trying to tell me something,” she recalled. “And then that moment I felt charged by the ancestors to tell their story, and I was terrified because as I mentioned I had only written contemporary fiction and so it felt like a big charge.”

That charge became Yellow Wife, a novel of historical fiction inspired by the life of Ms. Lumpkin and the Lumpkin jail. The book follows the life of Pheby Delores Brown who was born and raised on a plantation in Charles City, Va. She was shielded in part from the trials and atrocities of the time by her mother’s role as a medicine woman until she finds herself at Devil’s Half Acre, a notorious slave jail in Richmond, Va. In a place where many are broken, Pheby learns to survive.

Ms. Johnson dedicated the book to her children with the inscription: “To know where you are going, you must understand from whence we came.”

“I always know the dedication, like right in the beginning of writing the book,” she said. “When I said yes to it, I’m like, okay, this is the book for the children because this is the piece of literature that if they don’t read anything else I write . . . this is the book that I want them to say yes to.”

Ms. Johnson conducted extensive research, going on plantation tours, reading slave narratives and spending a lot of time at the Library of Virginia.

“It was also very gratifying for me to be able to flip back into history and kind of try and get a glimpse of what it was like for our ancestors during this time.”

The story is a blend of reality and fiction due to the lack of saved history about Ms. Lumpkin.

“Women like her have been blotted from our history and so I would find bits and pieces of her and then I would find bits and pieces of other women who were in similar circumstances as her, and then I would use my imagination to weave all of that together to create the story,” Ms. Johnson said.

Ms. Johnson tried to use as many facts as possible when writing the book. When she needed a name for a character, she would look to plantation ledgers and individuals who ran the Richmond slave trade.

“The point for me was to honor as many ancestors as possible. So even though the story was largely inspired by Mary Lumpkin in the Lumpkin’s jail, there were so many little snippets of stories that I found in my journey of researching that I thought it was important to get those stories in.”

She would also weave other slave narratives into her story. The character of Essex Henry, Pheby’s long loss love interest, was largely inspired by Anthony Burns.

“He was born in Virginia but he escaped up to Boston, and then was brought back to Virginia under the Fugitive Slave Act,” Ms. Johnson said. “He was brought to the Lumpkin’s jail where he was held in the garret room for four months and Mary Lumpkin took pity on him and snuck him a hymnal. And when I read that, I thought, wow, that is the beautiful beginning of a love story.”

All Ms. Johnson had to do was place Essex on the plantation with Pheby and then let their story play out naturally.

Although she was able to find honor in writing Yellow Wife, the difficulty of the subject matter weighed on Ms. Johnson.

“I spent three years with this novel, and three years reading books about enslaved people and doing the research and that’s a dark place to be. I had to take breaks, take some time off in between certain scenes and writing.”

But she persevered and found strength in her protagonist.

“For me I always look at the character that I created, Pheby Delores Brown out of Mary Lumpkin, and I think my goodness, if she could endure then, certainly I can do whatever. The world is completely and utterly open to me, there are no excuses. There’s no reason why I can’t be successful or why I cannot succeed.”

Sadeqa Johnson will take part in a panel discussion Friday at the Martha’s Vineyard Museum with Deesha Philyaw and Torrey Peters titled Mothers and Daughters. The event is moderated by Dawn Davis and begins at 2 p.m. She will also  participate in an author talk with Angela Ards on Saturday at the Chilmark Community Center, beginning at 11 a.m.