No matter how sneaky or careful I am, if I return downstairs from anywhere upstairs in the mansion, the guards go hostile. The guards outside are fine. Is this a bug?
I will do a bit more experimenting, but I've tried coming in through both the rear staircare _and_ the front door. I haven't killed any guards, AFAIK, but have knocked many out on the upper floor; I wonder does doing that make them all hostile?

P.

Lots of people seem to have this problem, but it hasn't happened to me yet, and I routinely kill/knock out all the upstairs guards. When you mention being sneaky, do you mean you were sneaky the whole time you were upstairs? One theory is that if anyone downstairs hears you skulking around it will turn them hostile.

Party Guests are forbidden from going upstairs, unless you're with a Boyle.

Sure, but surely the downstairs guards should only go hostile if they see me coming from upstairs? They seem to have a supernatural ability to figure I've been up there...

P.

Happened to me in one playthrough. Suddenly 2 patrons out of 3 downstairs was terrified by Corvo and it just became impossible to not kill anyone as every guards would come running. I had to reload my game from the mission start.
No idea what happened.
I had been sneaking around upstairs, essentially to grab some money and see how I could deal with the randomized Boyle I got... AFAIK no knocked out guards were discovered, but it's highly possible that they noticed some of them were missing from their patrol duties...

There's another thread about this too. I didn't get it, but I do get the thing where even if I kill someone without being seen, once the body is found everyone knows it was me. Not sure if that's a bug or just a design limitation. A shame that the boyle mission wasn't expanded if that is indeed the case.