Post-Victorian era New York City was quite the tale of two cities—the best of times for the comfortable Park Avenue elite, but the worst of times for the tenement-dwelling immigrants that held down the Lower East Side.

That doesn’t mean the wealthy were safe from the seamy elements of the city’s underbelly, that place a few miles south but also worlds away. An educated and affluent person could unwittingly get sucked into a frightening world of crime, and the most powerful families could hold close alarmingly dark secrets.

Such a status is part of the city’s history, but in the case of Roxbury author Cuyler Overholt, it’s the stuff of great historical romance and mystery.

Her first book of fiction, “A Deadly Affection,” takes place in 1907 in New York City. It tells the story of Dr. Genevieve Summerford, a young medical psychologist (psychiatrist in modern parlance, but a century ago that term had a misleading connotation relatable to the criminally insane) who worries that she unintentionally provoked a patient to commit murder.

With the help of a shady Tammany Hall captain (perhaps a redundancy), Dr. Summerford attempts to prove the innocence of her patient. Along the way, she uncovers a nasty secret about one of the city’s most powerful families. And therein yet another conflict is found: the secretive revelation means certain catastrophe for loved ones, but the truth could set her patient free.

“I’ve always been intrigued by this era, and then I found myself gravitating to this era,” explained Ms. Overholt on why she penned a murder mystery around Teddy Roosevelt’s Manhattan.

The author’s grandmother was, in fact, a New Yorker from a well-to-do family of a bygone era, so a personal connection already existed. Perhaps that familial familiarity gave Ms. Overholt an innate interest, but to bring this 452-page tome to life a massive amount of research was required.

It took a number of years to complete, and her meticulousness didn’t speed the process at all. But that’s better than a mistake, even an otherwise forgivable one she would deem unforgivable. After all, as a war film, Mel Gibson’s “Braveheart” is worthy of high praise, but as a history lesson the details are grossly inaccurate; the kilt fashion, for instance, didn’t take Scotland for about 300 years after the death of William Wallace.

“In a way that’s just me, I’ve always been a perfectionist. But it is also the legal training,” said an author who is also a former attorney. “I wanted it to be accurate, and it was like being on a treasure hunt.”

For example, she spent a whole day trying to figure out if the blue laws of the time would allow a brewery employee to drive a wagon full of empty kegs on a Sunday. It’s a small detail, but that’s where the devil may lie.

The story references the electric chair for the supposedly murderous patient, but is that historically right? Yes, this form of execution was first used in New York—first used anywhere—17 years prior to the story’s setting.

This attention to detail is what allowed ForeWord Clarion Review to say the book “shines like a star in a highly competitive genre.”

As for the notion of a woman practicing medicine 105 years ago, it seems the glass ceiling actually shattered around the turn of last century, but for a brief time, and then was wrongly brought back to original form for generations to follow.

“There was this window of opportunity, where medical schools were opening to women,” explained Ms. Overholt, supporting the historical truthfulness of the story. “There was this heyday, but then it closed.”

That window was open again by the time she was ready to matriculate.

After Trinity College in Hartford, Ms. Overholt followed a notion to the University of Virginia Law School. She graduated there in 1979, and spent a few years writing briefs and memoranda. Maybe not the most celebrated position in the field, but she enjoyed the writing aspect.

Still, the job proved not to offer the kind of creativity she wished to explore, and by 1984 she had exited the field. Ms. Overholt opened a freelance writing business that year, and worked for about a dozen more in that industry. It involved a lot of technical translations from mediations, and a lot of writing about engineering practices, things that needed to be translated to trade journals.

For the past 25 years, the Fairfield County native has lived in Roxbury with her husband, and it is where they raised two boys. She worked in the freelance business until 1997, and at that time decided that if she was ever going to move into fiction, her own passion, then it was the time.

The events of 9/11 changed something in her, though, as it did so many people, and she sought her own form of constructive therapy: house-building.

It’s been a circuitous path, but it seems to have been a most worthwhile trek. And an edifying one; even Ms. Overholt is amazed about the things she learned while researching the period described in her book.

“I learned a tremendous amount. I like to go back and read the newspapers of the time,” Ms. Overholt said, noting that publications of the era offer a truer picture than some contemporary books. “After a while, what surprised me the most is that people then were not the much different from us.”

The atmosphere may have been foreign, but the motivations and desires of the people in the early 20th century were surprisingly similar to the motivations and desires of the people in the early 21st century.

“The United States was just coming into its own,” Ms. Overholt said, describing the era shortly before the Great War. “It was nice to discover things that move us now haven’t changed that much.”

Things like finally writing a nice historical mystery.

Ms. Overholt will be signing copies of “A Deadly Affection” at the Hickory Stick Bookshop in Washington Depot at 2 p.m. on Sunday, April 22. The book is published by Copper Bottom Press and has a cover price of $16.99. For more information, see the Web site at cuyleroverholt.com.