Helen Keller's life story has been told and retold through different versions, all based on her book The Story of My Life. The Miracle Worker is a three act play that begins with Helen's illness and her mother's discovery that Helen has been left blind and deaf. By the end of Act I, Annie Sullivan has arrived and, despite her family's misgivings - "do they expect one blind child to teach another?" - Annie will prove to be a match for Helen in establishing her right to teach her.
In Act I, scene viii, Annie, having just arrived, allows Helen to open the case with Annie's key and mimic in front of the mirror. Annie wastes no time and immediately begins to "spell" to Helen. Everyone is skeptical of her and doubts her ability to help Helen who soon has a temper tantrum and, taking the key and locking the door, leaves Annie locked in her room. Annie will have moments of doubt, when her young (deceased) brother will preoccupy her thoughts but her strength of character will prevail.
At the end of the act, unbeknown to Helen, Annie will see Helen throw the key down the well. This is symbolic as Annie will never be defeated and now accepts the challenge; she has already begun to understand and respect Helen.