When leaving Kiwu's area, turn right and then right again, the door should be lit up. Provided you put the sleeping potion in the food, he should be the only one in the room. The quest finder will mislead you and guide you to the cobra's head which is an empty area.
If all else fails, check your map, which should accurately show the locations of people. You do need to put the sleeping potion in the food first or you will be fighting a lot of kroks along with him...
