The title character of Ellen Foster is a headstrong eleven-year-old girl who suffers much abuse in her young life. She is sexually abused by her alcoholic father, and, as he is unemployed and very seldom at home, she must adopt all household responsibilities, such as paying bills, shopping, and cooking. Ellen adopts these duties without complaint, though she realizes that most children have loving parents that do take care of them. Shortly after her mother commits suicide, Ellen can no longer stand her father's incessant sexual and psychological abuse. She knows she deserves a loving home and family and first tries to stay with her aunt Betsy, who, after Ellen stays for the weekend, tells her that the visit was only meant to be temporary.
At school, Ellen's teacher asks her how she had gotten the bruise on her arm. Ellen is not at all reluctant to tell her that it was her father who put it there, and, after a brief conference, the teachers decide that Ellen will live with Julia, her art teacher. Ellen's short but happy stay with Julia comes to an abrupt end when her wealthy but cruel grandmother wins custody of her in court. Ellen is extraordinarily precocious and understands that her grandmother's cruelty is a means to get revenge on her father, whom her grandmother despises. Ellen's stay with her grandmother highlights her acute self-awareness and her will to survive despite the worst odds. Her grandmother is constantly reminding Ellen of how much she is like her evil father, which scares Ellen into questioning her body and her character. Very seldom does her grandmother speak to her, except to berate her about her likeness to her father.
Almost immediately, Ellen's grandmother puts her to work rowing the cotton fields that she owns. It is there that she meets Mavis, a kind-hearted, black field worker who helps her to learn that it is character, not skin color, that is important in a person. Ellen also learns this lesson from Starletta, her black best friend. However cruel her grandmother is, Ellen still cares for her with the utmost tenderness when she falls ill. Ellen is unusually forgiving and loving, especially considering that she has suffered a life absent of love, and hopes that her grandmother will be welcomed into heaven despite her cruelty.
After her grandmother's death, she is sent to live with her aunt Nadine and her cousin Dora. She is miserable with them, as they are both utterly false. They pretend to be wealthy and successful, and they are condescending to Ellen for coming from an impoverished background. She cannot tolerate their falsity, as she is an honest, matter-of-fact character. Never once does she sugarcoat her story to make herself seem better than she is; she simply says what she sees and what she feels. Throughout her hardship, she is determined to find a home and family to love her and is confident that, somewhere, one exists.
Upon first sight of her new mama, Ellen knows she will be the one to take her in and love her, which she eventually does when, after being kicked out of Nadine's house on Christmas day, she bravely walks across town, knocks on her new mama's door, and asks her if she will care for her. In return, Ellen offers her one hundred and sixty six dollars—her life savings—which new mama refuses. This scene denotes Ellen's inherent sense of fairness and equanimity, which is evident also when she invites Starletta to stay over her house for the weekend, as she feels she must repay her for her kindness. Overall, Ellen is a remarkably precocious, determined, and intelligent girl far wiser and wittier than the average eleven year old.