The main character is a girl in a wheelchair who can't remember her past or walk. Her name is Anna or Hanna, I think. She is adopted by new parents and visits an old boarding house and remembers her past and the ability to walk. She goes back in time to see her parents. She also goes back to the 19th century and rescues a boy from slavery and brings him forward to the current day.
I think it was published in the mid 1990s.