Night Huntress Book 3. At Grave's End

It should be the best time of half-vampire Cat Crawfield's life. With her undead lover Bones at her side, she's successfully protected mortals from the rogue undead. But though Cat's worn disguise after disguise to keep her true identity a secret from the brazen bloodsuckers, her cover's finally been blown, placing her in terrible danger. As if that wasn't enough, a woman from Bones's past is determined to bury him once and for all. Caught in the crosshairs of a vengeful vamp, yet determined to help Bones stop a lethal magic from being unleashed, Cat's about to learn the true meaning of bad blood. And the tricks she's learned as a special agent won't help her. She will need to fully embrace her vampire instincts in order to save herself—and Bones—from a fate worse than the grave.