Well let's reason this Justin thing out, as I think it would require a lot of assumptions.
1) Justin was a contemporary of Margaret's. He might have visited and Thomas could have seen him, but he would have been young. Depending on if DuMorne still had contact with Raith after Margaret left, Thomas could have easily been old enough to know him.
2) We also have to assume that Thomas never mentioned to Harry that he knew his abusive adoptive father, because that kind of info would have been shared with the reader as foreshadowing.
4) We have to assume Justin is good enough to enthral Thomas. We know he has experience with it, as he did it to Justine. And Thomas seemed to be weak, so maybe he would be susceptible. We could alternately assume he blackmailed him or something, but Thomas just going with that seems unlikely.
4) We have to assume that DuMorne would expose himself to Thomas in the process, rather than keeping his identity hidden under a cowl or something.
5) We have to assume the payoff would be worth revealing himself and revealing he was still alive. I could see where Thomas dying in the attempt might be a safe assumption, but it seems awfully risky, because there are a ton of people in town that would be able to examine Thomas and see that he was manipulated.
Ive been racking my brain to try and figure out who of Harrys enemies has a name that starts with J
Not many. I was looking earlier. Really just Justin, or the Jade Court (doesn't seem like something an isolationist faction would do, unless Nemfected?), or the Genowska (sounds like J to start with), or Jenny Greenteeth (dead but maybe not?).
