Annabel Starkey has escaped Liverpool in the industrial North of England and established a sedate, respectable life teaching English at a school in the old University town of Cambridge. When a pupil is found murdered and drained of blood, on school premises, Annabel finds that the darkness in her own past will not stay buried. As the murders continue, she discovers that Jonathan Grey, a friend and fellow teacher, is more than she had thought. Jonathan has been searching for a way to atone for the death of his brother for nearly two centuries, sustained by a monthly ritual celebrated in human blood. And he believes that the murderer is a vampire like himself - but one who lacks his own scruples. As Annabel and Jonathan follow the trail of blood into the darkness buried within an ancient Cambridge college, Annabel discovers that many of the things she had been told about vampires are untrue, but that others fall short of the full reality. Finally faced with by even darker force that uses human suffering and death to power its magics, Annabel and Jonathan find their faith and determination stretched to their limits as they discover that evil lurks in every human heart.
"evil lurks in every human heart" is like saying they discover everyone breathes. True, but pointless. Be specific. You might focus on what the vampires scruples are; I didn't know there were rules. And what did Annabel think that isn't true?
This plot is pretty whiskery; you'd do well to give us something with a fresh perspective.