Netflix’s Monster: Who is Emma Borden? All about Lizzie Borden’s elusive sister and their fallout

Netflix's new anthology installment, Monster: The Lizzie Borden Story, premiering September 17 with Ella Beatty as Lizzie and Billie Lourd as her sister Emma, is bringing fresh attention to a figure often overshadowed by the case's central suspect. Emma Borden spent decades tied to one of America's most infamous unsolved crimes, first as her sister's staunchest defender, later as an estranged relative who walked away.

An older sister's promise

Born in 1851, Emma was the eldest of the Borden children, nine years ahead of Lizzie. A third sister, Alice, had died in infancy. After their mother's death, Emma reportedly promised on her deathbed to watch over her younger sister, a vow she seemed to honor for much of her adult life. She was also protective of the family's reputation more broadly; in a 1913 newspaper interview, she pushed back hard against characterizations of their father as stingy, dismissing the idea outright.

Miles away when it happened

When Andrew and Abby Borden were murdered in their Fall River home on August 4, 1892, Emma wasn't there. She was some 17 miles away in Fairhaven, staying with a friend. It was Lizzie who had a family physician wire Emma the news once Andrew's body was found. That absence gave Emma an alibi Lizzie never had, and it's part of why Emma was never seriously considered a suspect, even as her sister became the face of the case.

After Lizzie's acquittal, Emma didn't distance herself. The two went on living together, eventually settling into a large home called Maplecroft, largely cut off from a Fall River society that had turned on them after the trial.

The sisters' bond didn't survive the years that followed. Lizzie grew close to actress Nance O'Neil and began welcoming theater friends into Maplecroft — a shift that apparently strained things between the two women. In 1905, Emma left the house for good.

Neither sister ever fully explained what drove them apart. Years later, in that same 1913 interview, Emma described the situation before her departure as having become unbearable, hinting at a slow deterioration rather than a single breaking point. Beyond that, both women stayed largely silent on the matter.