A little girl is left on a dock in Brisbane, Australia after a large ship from England has finished unloading its passengers. She is holding a white leather suitcase. There is no one to fetch her and no identification on her. The dock master takes her in his care and when no one comes looking for her, he simply takes her home.
Thus begins the mystery. Who is this child and how did she get there? The child herself is not able to provide information. She simply tells him she was told to hide until the Authoress comes for her. The dock master and his wife raise her as one of their own. They don't tell the child how she came to be in their family until the father is old and dying.
The story, of course, sets out to solve this mystery. We have the story of the little girl, whom they call Nell. We have the story of her granddaughter, Cassandra. We have the story of how they individually go to England to try to solve the mystery. And we have the story of the little girl before she was hidden on the boat.
If you like puzzles, then this is the story for you. If you don’t want to work a little in order to savor the richness of the story, then perhaps you would like something else. Here's a description from the author herself.