In order to stay human, Audrey has built a moat around herself; a moat of books, music and dreams.
It makes her different from the echoes: the sophisticated, emotionless machines, built to resemble and work for the humans.
Daniel is an echo - but he's not like the others. He has feelings he was never designed to have, and cannot explain. And when Audrey is placed in danger, he's determined to save her.