Who is Jane Elizabeth Johnson (aka Jennie Spring) from The Voice on the Radio and what is their importance?

Jane Elizabeth Johnson (aka Jennie Spring) from The Voice on the Radio is the girl that was kidnapped when she was a young child. She was taken by a girl named, Hannah, who had gone to live with a religious cult for many years, estranging her from her real family. She shows up on her parent's doorstep years later with Jennie in tow and tells them that she is her daughter and that they would be better parents. As far as Jennie has every known, they were her real parents.

It isn't until she sees herself on teh back of a milk carton that she starts asking question. In this book, she has already been introduced to her birth family and is trying to assimilate herself back into their lives.