Charlotte Brown affirmed to be a prisoner of Bergen-Belsen who was too sick to tell anyone her name when the Allies freed the prisoners of the Nazi camps. She was then relocated to England, where she was back to some semblance of health. Afterwards, she kept to the streets in Germany as a pickpocket and a thief until she met a soldier, Private William Snow who married her and the two lived in New Jersey until William was called back to service during the Korean Conflict and was killed there in 1952, leaving Charlotte a widow. In the same year, Anne Frank's diary was published in America. At first, she wanted to reunite with her long lost father, but refrain from doing so because he started a new life with a new family and because people started to acknowledge the Nazi's heinous crimes.
Personality and Appearance
Charlotte Brown is a delusional woman who believed herself to be Anne Frank. She has shown to be very knowledgeable having known to know detailed facts about the war, and the concentration camps. Having accused Dr. Arden of being a former Nazi, and this was later proven to be true suggesting she herself was in a concentration camp, that Dr. Arden was positioned at. She shows similar physical traits with Anne Frank, having dark hair, and similar eye color; this, and the facts she knew about the war; lead Sister Jude to actually believe that Charlotte was Anne Frank.
A woman, claiming to be Holocaust victim and diarist Anne Frank, says that she holds a secret about Dr. Arden's past. She insists that he is cruel Auschwitz doctor Hans Grüper. She confronts Arden with a gun lifted from a visiting homicide detective and shoots him in the thigh before discovering the legless and mutated Shelley. 
She holds Arden at gunpoint and demands to speak with Sister Jude but she is subdued by Frank. A man visits the asylum and explains that she is his wife, Charlotte Brown nee Cohen. He tells the tale of her descent into madness and Sr. Jude, in order to protect her from Arden's retaliation, arranges to discharge her into her husband's care. After she attempts to suffocate their infant son, her husband returns her to the asylum where Dr. Arden recommends a transorbital lobotomy. She is again sent home to her family, docile, happy with her baby, and apparently, without memory of her belief, she is Anne Frank. On her wall, with various other Holocaust photos and clippings, is a picture of Adolf Hitler and a young Nazi with an incredible likeness to Arden. 
- She was named Kassie in pre-air cast listings.
- Charlotte Brown is the only character played by Franka Potente in the American Horror Story franchise.
- Given the end of "I Am Anne Frank: Part 2," it is likely that Charlotte Brown was really Anne Frank, or at least one of the prisoners in the Auschwitz concentration camp, as she recognized Dr. Arden for who he really was. In fact, there is no doubt that Dr. Arden is an alias taken by Hans Grüper to escape justice.
- Private William Snow, Charlotte's first husband shares his last name with former Council witch Myrtle Snow, and with Rhett Snow, an Uber driver.
- To Mr. Brown: "Never been happier."
- Charlotte (to Sister Jude): "People finally started to pay attention to what they'd done to us. All because of a martyred 15-year-old girl. She had to stay 15. And a martyr. I could do more good dead than alive."
Sister Jude: "Your story is indecent."
Charlotte: "No, you are indecent. You have a Nazi war criminal working here."