Back with Baranor to rescue some prisoners. It's like they're playing your song.
Free the prisoners as per usual. Note that they don't seem to take any damage from area attacks (a useful trait in a soldier).
Free them all and you'll be faced with two captains. One is the Prisonmaster who's just captured Baranor, and the other is the backstabby component of this particular trap.
The final objective of the mission is to take down the two captains. It's wise to focus on the ambusher first- he'll be the more mobile and aggressive one. You've got plenty of room to range around, so try to separate them before bringing the place down.
When the last captain falls, your mission ends.