Dahlia considered for a moment. Telling him her reason for torturing him was only a bad idea if he could do something about it. It was pretty clear that he couldn't.
"Human pain can call demons from their world to obey someone with enough power, such as myself. I'm seeking out a demon because my daughter has taken up with an elderly vampire and I want him out of the way with the least trouble possible. Well, least trouble to me."
"As for why it was you, Mr... I mean Captain Harkness... Well, I hate to tell you this but you were just in the right place at the right time."
Dahlia scraped at the skin on the back of his hand with the edge of the knife, wondering if that would be enough to make him pass out.