An unlikely friendship between a reclusive Lizzie Borden and an international actor is explored in the latest edition of the Netflix series “Monster.”

Borden, who was famously acquitted of murder charges in the hatchet deaths of her father and stepmother in 1893, was living in relative seclusion in 1904 when she met Nance O’Neil, a theater and silent film actor who had performed all over the world.

In “Monster: The Lizzie Borden Story,” O’Neil (Jessica Barden) appears in four episodes, including one about Borden’s life after her acquittal.

Here’s what to know about their friendship and how it’s portrayed in the Netflix series.

Who Was Nance O’Neil?

O’Neil was born Getrude Lamson in 1874 in California, according to her 1965 obituary in The New York Times.

Beginning her acting career at 19, she took the stage name Nance O’Neil in homage to English comedienne Nance Oldfield and tragedienne Eliza O’Neil.

O’Neil was hailed for her theater performances as tragic heroines and performed on “hundreds of stages around the world,” according to her obituary. She performed in the United States, New Zealand, Europe and Australia, drawing notice for her performances in Broadway plays like “The Passion Flower” and “The Lily,” according to Deadline.

She later transitioned to silent films, where she appeared in dozens of movies between 1913 and 1932, per Deadline.

How Did Nance O’Neil and Lizzie Borden Become Friends?

O’Neil was starring in a play in Boston in 1904 when she met Borden, who lived in nearby Fall River, Massachusetts.

After watching her perform, Borden sent O’Neil a bouquet of flowers expressing her admiration for O’Neil’s performance, the actor recalled an article by the New Bedford Standard following Borden’s death in 1927.

Their friendship “purportedly scandalized (Borden’s) more retiring sister,” Emma Borden, author Cara Robertson wrote in her book “The Trial of Lizzie Borden.”

Following her acquittal in the deaths of her parents in 1893, Borden had remained in her native Fall River but became a pariah. She “lived virtually alone” with “few if any close friends,” according to her 1927 obituary in The New York Times, making O’Neil one of the few who got to know her.

Following her notoriety from the trial, Borden tried to recast herself as “Lizbeth” instead of Lizzie, which Miller writes “may have been O’Neil’s influence.”

O’Neil was one of her few friends, but the relationship only lasted for a couple years. A 1905 story in the San Francisco Call reported O’Neil and her acting company giving a performance at Borden’s Massachusetts mansion named Maplecroft, where she lived with her sister, Emma Borden.

The story reports that O’Neil was an “intimate friend” of Borden’s who had met her a summer earlier at a resort near Boston. Their friendship lasted until O’Neil finished her theater season in the Northeast before she went on a national tour, according to the New Bedford Standard.

There were rumors of a romantic relationship between the two, but no definitive proof in any letters or writings by either woman. Their relationship was also dramatized in the 2010 theater production “Nance O’Neil.”

Borden never married, while O’Neil married British actor Arthur Hickman in 1916 and remained with him until his death in 1931.

O’Neil told the New Bedford Standard that Borden seemed “utterly lonely,” while noting that Borden’s notoriety for the murder trial did not matter to her.

“It did not alter our relations in the least,” she said. “Of course, the tragedy itself was never mentioned between us; never was there ever so much as an allusion to it. I simply felt a great sympathy for her, and a great deal of admiration for the way she carried on. She was always so alone.”

Borden, who secured a large inheritance following the death of her father and stepmother, may have helped out O’Neil financially. She helped her get out of debt to creditors and her manager, according to The Lizzie Borden House.

The two did not keep in touch after O’Neil resumed acting around the country and internationally.

“We were like ships that pass in the night and speak to each other in passing,” she told the New Bedford Standard.

How Is Their Friendship Portrayed in ‘Monster’?

Aspects of their friendship, real and imagined, appear in “Monster: The Lizzie Borden Story.”

Borden, played by Ella Beatty, is first shown seeing O’Neil onstage at a play in Boston.

“She’s enchanting,” Borden says.

After Borden greets O’Neil following the play, she asks her to dinner at her home.

O’Neil pops up in another episode in which she is shown imparting dramatic techniques to help Borden prepare for being on trial in the deaths of her father and stepmother.

It’s impossible for that sequence to have happened because the two didn’t meet until 1904, 12 years after the murders and 11 years after Borden’s acquittal.

In the final episode of the show, which details Borden’s life following her acquittal, Borden shows O’Neil the manicured landscaping and her menagerie of animals around her opulent Maplecroft estate.

O’Neil regales guests at dinner with her tales of performing in Europe, Egypt, Hawaii and Australia. The rumored financial relationship between Borden and O’Neil is also dramatized in the episode.

“Lizzie, it was your patronage that enabled all of it,” O’Neil tells her on the show. “Traveling first class, accommodation worth of a star, and I owe it all to you.”

O’Neil then talks about how she wants to leave the stage to do silent movies in the burgeoning motion picture industry. She also tries to hit up Borden for more money.

A rumored rift between Borden and her sister, Emma, over Borden’s friendship with O’Neil is also hinted at during a dramatic scene at dinner.

Emma Borden, played by Billie Lourd, castigates her sister in front of her dinner guests while calling O’Neil a “pig-s--- actress.”

Emma Borden never spoke about the reason for her rift with her sister in their later years that caused Emma to move out in 1905, so there’s no record that it was caused by O’Neil.

“The happenings in the French Street house that caused me to leave I must refuse to talk about. I did not go until conditions became absolutely unbearable,” Emma Borden said, according to Lizzie Borden’s obituary.