I read it somewhere that "If you have talked with Delthyr in the Eastern part of Baldur's Gate you'll meet him once more on the first floor of THREE OLD KEGS. He tells you to follow Rashad, Duke Eltan's healer, each night when he leaves the Flaming Fist Castle to see where he goes".
The question is: When does he leave the castle? i have had awaited outside of FF castle in night for some minutes for him to leave but he never did leave the castle. (I know that he is inside because i can enter the castle and see him in there)