That is bugged...
With D2:DC you can at least use the Developer Mode cheat window to leave the house. You could try teleporting to Caracalla and see if that would trigger his conversation and end the quest.
You can also try emailing supportdks@larian.com, with a description of the problem (see the DKS
support page). With your save they may be able to fix whatever is wrong with the quest.
Alternately, it is possible if you reload a save before entering the room with the ghosts and do other stuff for awhile, this quest may work properly when you get back to it again.
In XP the saves are in the folder
C:\Documents and Settings\ %username% \Local Settings\Application Data\Divinity 2\Savegames
or in Vista / Win 7
C:\Users\ %username% \AppData\Local\Divinity 2\Savegames
You may need to set Windows Explorer to show hidden files and folders (
XP, Vista,
Win 7).