When she was 18 months old, she got a disease, causing her to go blind and deaf. Then, she had to live like that until another few years, until a person named Anne Mansfield Sullivan came to her and taught her.
With the teacher, Anne Mansfield Sullivan, Helen learned a few words, including "doll". She got confused with "water" and "mug", though, so her teacher brought her to the well-house.
When Keller went back from the well-house into the building, she remembers the broken doll she threw on the floor, sad at what she did.