You can begin this quest only during the day. After defeating Bakir's men, you must use Compel Soul to interrogate the corpse of the man the soldiers were interrogating.
Turns out the headhunters's unit I dealt with was looking for a secret manumit stash. The rebel they captured wouldn't tell them a thing - but I managed to pick up a trail where they failed. Seems like I should look down the old well...
To get the information, you can use two items. The first of them is the Interrogation Instrument, which you will find right next to the corpse.
The second item is Manumit's Bandana, which you will find on a wooden bench, right next to the entrance to the house.





