Teenage magi Adrienne Young kills monsters, protects the innocent, and sometimes passes chemistry. But when she kills a hellhound that's been haunting college campuses she draws the attention of Hecate, a banished goddess seeking to restore her power and return to the mortal world. As Adrienne digs deeper, she uncovers Hecate's murderous plot and vows to kill her once and for all. When Hecate sets her sights on Liza, Adrienne's sister, the fight turns personal. With a band of unlikely allies and time running out, Adrienne may have to choose between saving the world or saving her sister.