Hey, I appreciate all of you getting back to me so quickly. I'm stil kind of new to BGII as I played it through once and am doing so again, now, after about a year away.
My party's rep. is pretty high, and my character is lawful neutral - and I wasn't romancing Aerie at all, I nipped that in the bud early. (I didn't feel like putting up with the drama and having her leave me in the lurch at some critical moment.) Also, H'D didn't say anything before turning on me - it was in the middle of the fight with Samia, after all - though I know dialogue can interrupt pretty much everything.
Any more thoughts? I've kind of resigned myself to going back to my most recent save before H'D's treachery and starting over. (Unfortunately for me I think that that's just prior to entering the room with the archers behind the wall - I quick-save all the time and overwrote the one right before battling Samia...)
A question - what do Ctrl-Q and Ctrl-Y do? Sorry to ask stupid questions, but how else is this dingbat going to learn?
