On the evening of her seventeenth birthday, Katie receives an ultimatum from a vampire—she must find the mysterious ghost girl or lose the life-saving cure that was given to her. The only trouble is the ghost girl is just a legend—she doesn't exist.

At the same time, Katie's sleepy hometown of Elspeth's Grove begins to be plagued by ghosts, and Katie learns that the ghost girl may not be that illusory after all. As Katie sets out in pursuit of the phantom figure, her beloved William follows her. But Katie is determined to keep him out—the cure she is trying to protect was given to her for William.

Katie's search is further complicated by the fact that she has lost her powers. Will Katie get her powers back in time? Or will the mysterious ghost girl prevail?