The film entitled Piano Teacher is about the life and experiences of Erika. Erika is a lady in her forties who works as a piano instructor in a music school. She lives with her mother and her father is a lunatic and lives in a care home. Apart from being a teacher, Erika has a very complicated private life. She suffers from sexual repression. This causes her to live a very desperate and unfulfilled life. She resorts to masturbation and watching pornographic movies.
Erika comes across Walter. Walter is a seventeen year old engineering student. Erika becomes obsessed about Walter. She tries to overcome her feelings for Walter to no avail. She even tries to avoid getting close to him but this fails and Walter becomes Erika's student. Erika later finds out that Walter is very close to another student named Anna. She becomes jealous of Anna and decides to hurt her.
Erika places broken pieces of glass in Anna's coat pocket. These wound and damage all the fingers on her right hand. Anna becomes deprived of performing at an upcoming musical concert. Anna's mother comes to the school and asks Erika for advice on how to treat her daughter's hand. She even asks Erika who would be so wicked to do such a thing to her daughter and Erika keeps quiet.
Not long after, Walter follows Erika into the ladies' toilet. He expresses his desire to be with Erika and starts kissing her. Erika rejects him at first but later gives in and responds. Walter tells Erika he wants to start a relationship with her but Erika rejects his idea. Afterwards, the two finally start dating.
One day Walter attacks Erika in her house, beats her up and even rapes her. Erika is not happy about the situation and realizes she deserves to be treated better than that. The film ends during a concert whereby Erika stabs herself with a kitchen knife.