Melanie Stryder is a human. For long after the Souls invaded, she hid with her younger brother and an older human, Jarod, whom she met along the way. When she wanders off to find family, Malenie is captured and a soul is placed in her body.
Normally, the souls have no problem pushing away the human inside, erasing their thoughts completely, but this is no normal situation. Wanderer, a female soul who was placed in Melanie's body, can't get rid of her thoughts. Melanie is a fighter, and Wanderer is afraid that she will soon regain all control.
Because of the memories that Melanie has shown Wanderer, the soul has fallen in love with Jarod, just as Melanie did, and loves the brother Jamie as her own. They set off in the desert, desperate to find Melanie's crazy Uncle Jeb, hoping that Jarod and Jamie will be there as well.
After near death, they finally make it, but Wanderer is not accepted by most of the humans- including Jarod. In spite of Melanie, Wanderer doesn't tell the humans that she isn't alone in the body, but a few of them guess for themselves.
Wanda (Wanderer), must try her best to live in a place where she is not accepted- and it only gets worse when she developes a friendship with not only Melanie, but another human named Ian.