She is being hunted by her sire, the vampire who bit her, so he can finish her off by either changing her completely or killing her, as well as a demon. Teaming up with some friends she starts hunting both.
Throughout the story there are side plots and stories but in the end they are all tied together. A very good read, and I've ordered the next two in the series so that I can read more about Celia Graves! If you want a vampire book where the vampire doesn't sparkle, but needs a stake in the heart, holy water squirted at or beheaded, this is the book for you.