If you complete one of the quests that give you an invitation to the castle before doing the escort quest, the healers will move on their own. You'll find most of them in the Blue Boar inn. Mardaneus should still be there, though. Try running around the house if you don't see him; sometimes he likes to hide near walls until you get close. If the house is locked, just wait until you start the human council member quest and you will be able to complete the murder quest when you talk to him then.
Welcome to the forum.
BTW, there are separate forums for Divine Divinity and Beyond Divinity.
Angel
