The heart is a threshold science can't cross.
In the vampire-servant relationship, the vampire holds all the power.
Being Lord Brian's research assistant as well as his servant, Debra accepts that, but she craves her Master's heart.
When Brian notices his servant's unhappiness, he uses methods they both understand to prove just what belonging to him fully means.
Story Witch Press The scientific method: a vampire queen series novel, paperback/joey w. hill
