I'm supposed to go to the kingslayer's hideout now, as part of the Assasins of Kings quest, but I just can't find it. The quest marker points to a cave system near the army camp, but the hideout is nowhere to be seen there. The hideout itself has a very recognizable door (as you saw in the vision), so it should be easy to identify once you found it.
Am I not looking thoroughly enough or is the quest marker in the wrong place?