Ada is special. Her parents have always told her that she is a fairy that had one wing broken when she was born, and that's why she is missing an arm. When she was little, she believed it; now that she is about to be 11, she doesn't believe it anymore, but she likes the story so much that she lets her parents keep telling it and she even makes them questions, so they come up with more details about her birth.
But this birthday is going to be special. She is going to celebrate it in a camp, where she is going with her school, and it's possible that she might discover all the truth about the fairies there.