Interrogation is a written note found in The Knife of Dunwall.
The interrogation chair is set up in the meat locker and fully powered. We have run some test runs on a few of the most problematic laborers. They spill all of their secrets very quickly. They seem to die easily after about 4 treatments. She is ready for you whenever you need her.
It can be found in the Rothwild Slaughterhouse during A Captain of Industry, either in Bundry Rothwild's office on his desk, along with the note Ames Negotiations, or in the records office near the note Shipment Manifest. Picking it up at one location will remove the other copy.