My thinking has been that whatever SA may have done to HD, it wasn't about any untoward interest in young girls or about his interest in slasher/horror stuff. But just about strongly disliking (not to put too fine a point upon it) HD with all his heart and knowing she felt the same about him.
So, just speculating, but what if something like this occurred: At Christmas dinner with CD and GF, HD says something like this, "Dad, I hate living with Mom and SA. What I want more than anything is to live with you guys. Why can't you get a job, divorce Mom, and make her and SA leave? You could move your clothes and stuff across the street, but you don't have to actually stay there every night. DD and I are old enough to take care of ourselves. Couldn't you just try, Dad? Cause that would make me happier than anything."
And suppose he says something like "Well, I hate to see you so miserable, so maybe I should start working on making that happen." Then, BD and SA learn about this on Sunday, when HD is back at home - they'd both probably be extremely upset if this could actually happen. Strong motive for SA to make HD disappear, imo. Especially if DD didn't particularly mind living with SA.
Do we know enough to speculate on whether that plan could actually be effected by CD? Like, would he be able to get custody of HD and DD? And would he be able to make BD and SA move out?
Thanks in advance if you can say whether or not CD could do this.
JMO