[voice]
[She noticeably hesitates-- part of her profession is keeping as many details from others as possible, and such ingrained habits are hard to break.
But if this is how to get the result she wants...]
There are a number of creatures called vampires in this prison-- and at least two of which have the ability to turn people into familiars of sorts. I don't believe he was entirely human to begin with, but someone I know was completely changed by one of them into a being similar to her. [...Is that enough]