I sorta came up with this cause I was inspired by my grandmothers tales of my family history before she passed away. I had learned that during the Salem, MA witch trials the accused witch 'Bridget Bishop' was an ancestor of mine. But anyways here's my general idea of what I had in mind.
My character is in fact a witch practicing magic and was caught dabbling in the dark arts, perhaps someone stumbles upon her in the middle of performing blood magic. Now this can go a supernatural way or natural...a man (either human or perhaps vampire) manages to capture her before the town does and hides her away for a price. Now that price can be anything. Power (if the man is human), perhaps control and uses her abilities for his own gain. If he's vampire could be easier to control her...compulsion or blood bond whichever.
If interested send me a PM and we can discuss the plot further.