When Joyce suffers from unexplained headaches, Buffy suspects Dawn may be harming her, but they discover that they were caused by a brain tumor. Buffy soon discovers that the Keys protectors had turned the Key into a human biologically related to the Summers — her new sister Dawn. At the same time, they implanted in her family and friends lifelong memories of her. As a result, Buffy, and especially Joyce, begin to accept Dawn as a true part of the family.