Who does the narrator meet? What is discovered about this person

While playing David meets a young girl, Sophie Wender. The third time Sophie slides down the gully, her foot gets stuck between two rocks when she lands. David attempts to assist Sophie in getting her foot out, and recommends to her that she remove her shoe. Sophie is crying and in much pain, but she is opposed to taking off her shoe. Eventually she realizes there is no other way to get her foot out, so she agrees to remove the shoe. David doesn’t notice at the time that she has six toes.