Off-limits is a written note found in Dishonored.
Transcript[]
Captain Briarmont,
I must ask you to speak with one of your men. Corporal Keyes reports to you, I believe. According to the morning duty officer, Keyes has been making his way to the basement, meeting with the Royal Interrogator. I have no idea what they discuss, but it's been reported that Keyes has an interest in the occult. Either way, I'm not an Overseer, so I don't give a fig for how he spends his time when he's not on duty. But keep him away from the torturer. The basement is off-limits to our men.
--Major Hocking
Location[]
A copy can be found in the guardhouse outside Dunwall Tower during the mission Return to the Tower.