Some of the most classic horror stories revolve around demon possession and the accompanying exorcism. This novel doesn't disappoint as the main character comes face-to-face with the demon inside another person and her own identity.
Ever since her mom committed suicide, Marin has had a special ability that allows her to see people's pain in the form of shapes and colors. She can't figure out if this is a blessing or a curse. In the meantime, she's doing her best to make it through school, which means avoiding Cassie who tricked Marin into a horrible experience months ago. When Cassie freaks out in the middle of mass, Marin's ability allowed her to see something odd inside Cassie right before the girl collapses in a seizure. Cassie's brother knows that something more than seizures is going on with his sister. Somehow there's a connection between the two girls, something that they need to explore if there's any hope of saving Cassie.
This book was an interesting experience into possession. While it deals with trying to save Cassie, it also dips into Marin's family issues surrounding her mother's death, coming to grips with her abilities, and typical teenage relationships. This novel has a nice balance and still proves to be creepy.