Stephenie Meyer creates a wonderfully vivid world in which the human race has been forced into hiding to avoid becoming the living carcasses for the "souls" which have taken over Earth. Melanie Stryder is one such human. She has the misfortune to be captured and to have her body invaded by one of these parasites. Melanie doesn't just fade away as most humans do though. The soul, Wanderer, is ashamed that she isn't strong enough to control the "wild" human and tries to keep this hidden. The struggle Melanie and Wanderer face to come to terms with each other cohabiting the same body and the journey they take to get there leaves the reader unsure who to root for - the selfless soul or one of our own.