Elwin, the quest starts when you find the wife. She is right up the back of Verona, past the castle where the Earl? is imprisoned and the way through to Montero. Instead of turning left to go to Montero, continue straight down the path past the Knight's tent shop. You can sneak by the guard on the gate and there are 3 small houses and a castle in there. The king's wife is in the first house on the right.
Important: After you get her back to Debir, talk to her again and a "revenge" quest is generated. I forgot to do this time and went back to storm the castle but i couldn't. Now i'll have to make anextra trip back to Debir.