She's a guest starring character portrayed by Laurel Lefkow.
Mrs. Isaacson is a Jewish woman with a distinct German accent. Her limited knowledge of English comes from reading Shakespeare works, as evidenced by the choice of her children's names. According to conversations between Marcus, Lucius and Esther, Mrs. Isaacson lived in a shtetl, a small Jewish town or village in Eastern Europe before emigrating with her husband to the United States. 
Tenement District on Hester Street, New York City, 1896. Mrs. Isaacson was painting fake roses in the dim light of her home whilst her sons, Lucius and Marcus were getting ready to go out. Talking in Yiddish, she asked where they were going since Marcus was using too much scent. The taller twin said they had police business to attend, and Mrs. Isaacson replied that they did not seem to be going to do police business. Lucius stated that their mother intended to say that Marcus "stink like a 10-cent whore", and Marcus, annoyed by his brother's joke, wondered how Lucius could know what smell a prostitute has.
Whilst Marcus arranged to turn off most of the candles and lamps, Lucius reminded their mami to turn off the candles before going to sleep. She protested, saying it was Shabbat but Lucius replied that it was not that night, and switched off most of the lights, likely to discourage burglars. 
During the following weeks, Mrs. Isaacson tried to understand what was happening between her children but, unfortunately for her, they faced the problem whilst she slept. 
A couple of weeks later, Marcus invited his girlfriend Esther for dinner at his home to introduce her to his mother and brother. During the frugal candlelight dinner, the guests shared part of their family history. Marcus said to Esther to tell how her family had contacts with the Old Continent, like his own. Esther then explained to Mrs. Isaacson that her grandfather was originally from Minsk, but that he had died before she was born and her parents had met when the families had already emigrated to America. Esther then asked why Marcus and Lucius didn't had name from the Bible as per Jewish tradition, and Lucius explained that they were named after characters from Shakespeare's Julius Caesar, a book his parents were reading to learn English before they were born. The choice of these names was to prevent both Lucius and Marcus from being victims of anti-Semitism. Esther commented that this was a beautiful story behind a name. Mrs. Isaacson, however, did not seem very friendly towards Esther, so the diners continued their meal in silence. 
Appearance and Personality Edit
Mrs. Isaacson is a middle-aged woman. With a slight build, fair complexion and gray hair, Mrs. Isaacson has clear eyes and a kind face. Her clothes are simple, chaste and practical. Mrs. Isaacson is a calm and thoughtful woman. She is linked to the traditions and family values taught by the Torah. Mrs. Isaacson is a loving and apprehensive mother who desires the best for her children. For this reason, she chose names not typically Jewish for her sons, in the hope that they would not be discriminated against. Besides being very religious, Mrs. Isaacson also has some artistic talent that she uses as a pastime.
- Mrs. Isaacson: "Vau geystu" (Transl. from Yiddish: Were are you going?)
- Marcus: "We have police business."
- Mrs. Isaacson: "Es tut nisht shmekn vi politsay business" (It doesn't smell like police business.)
- Lucius: "She means you stink like a 10-cent whore..."
- Marcus: "How would you know?"
- — A Fruitful Partnership
- Since Marcus likened Esther's upbringing to that of his mother, it's possible that the Isaacson family was one of the many Jewish families forced to flee from Eastern Europe, likely Belarus, to avoid persecution.
- In the novel, she has a younger daughter named Cordelia, after Shakespeare's King Lear.
- Ep. 2: A Fruitful Partnership
- Ep. 4: These Bloody Thoughts (Asleep in the background)
- Ep. 5: Hildebrandt’s Starling
- ↑ 1.0 1.1 E. Max Frye (writer) & James Hawes (director); (February 19, 2018); "Hildebrandt’s Starling". Episode 5.The Alienist. TNT
- ↑ Hossein Amini (writer) & Jakob Verbruggen (director); (January 22, 2018); "The Boy on the Bridge". Episode 1. The Alienist. TNT
- ↑ Gina Gionfriddo & Cary Fukunaga (writers) & James Hawes (director); (February 12, 2018); "These Bloody Thoughts". Episode 4.The Alienist. TNT