When I entered the Baron’s basemen, I used my stealthy rogue to sneak past into the larder room with the chest with the book that had the beacon clues.
I then sneaked to the beacons and got into the room with Kytheala’s Belongings triggering the cut scene.
I went out and triggered the confrontation with the fake baron.
after the battle, I was stuck. The exit out of the base was not there nor could I open the magnificent door of imperial style.
the quest tracker would not advance past “Find Kytheala’s Belongings.”
I loaded the save I made right when I entered the basement and went right to the confrontation cut scene and everything went smoothl. I was able to use the beacons to open the door got the cutscenes of Kytheala’s belongings and the quest advanced
That's what you get for being clever and sneaky!