I"ve played DG twice and both times have regularly dialoged with Serena but never got the dialog start which I'm told would allow me to somehow cure her of her being a vamp. I'm only going by others' comments here that such a dialog does exist.

Being at LVL 51 now, I'm considered a new start of SK as even on Master, the play is a bit easy. My team even took on Karstaag at Adept and did OK.

If I do restart, I tend to play DG first as otherwise I have to contend with the vamps croaking desirable NPC's, but want to this time not miss whatever it is that triggers the sub quest to cure Serena. Can someone give me walkthrough of when this sub quest triggers and how to make sure it does? TIA.