Traude Krueger is working as a piano teacher in a women's prison. While selecting new students, she meets Jenny Von Loeben. When she tells her she can't take any lessons because her hands are too rough and she is uncooperative, Jenny becomes enraged and almost kills the prison guard, Mütze, also one of Krueger's students. Then she starts playing the piano. Krueger listens from the hallway and, impressed by her talent, later offers Jenny lessons, but requires absolute obedience, including eating a sheet of paper. She tells Jenny never to play "that kind of negro-music" again. Jenny's adoptive father wanted to turn her into a Mozart-like child prodigy when she was young, but when she resisted going to further contests, he raped her. Krueger plans to have her compete again. While practicing, some inmates become jealous of Jenny, who doesn't seem to get punished for beating up the guard. Some of the prison personnel oppose giving her the freedom to play the piano. However, the prison director wants positive media attention for his prison. Jenny reaches the finals of a piano competition for players of 21 and under. Mütze transfers her to the cell of her rival inmates. They strap her hands to the bed with some cloth and set them on fire. Jenny severely wounds one of the culprits, and she is forbidden to enter the competition. Krueger learns that Mütze deliberately set up the conflict and she confronts him. Krueger resigns, and takes her piano. Mütze helps Jenny escape from prison with the piano so she can play at the competition. Jenny learns that Krueger has had contact with her adoptive father. Thinking he arranged all of it and that Krueger was just being bribed into teaching her, she rages violently. Krueger tells her about her own past, how she lost her great love, another woman, during the second world war, because she was a communist, and how she also taught her to play the piano. Krueger convinces Jenny to play at the competition, where, because the police have come to take her back to prison, she has only four minutes to win the support of the crowd. She deviates from the original plan of playing a piece by Schumann and plays a unique piece of her beloved "negro-music", including percussion, foot-stomping and reaching under the lid to pound the strings. When she is finished, the crowd erupts in a standing ovation.
