Black Heart (Vampirates #4)

There's a new ship of Vampirates roaming the seas, leaving a trail of fear and devastation in its wake. So when one of the Academy's most-esteemed pirates is suddenly slain, the Pirate Federation takes immediate action to train a special crew of vampire hunters. Young pirate prodigy Connor Tempest is placed at the helm, which means he is leading the fight against a vampire ship with one very important passenger: His sister.