In first mission, there is a place where you have to blow up the prison gates. I know you can knock down two nearby guards and still get the Ghost achievement. Is it also possible without the take down? There is smoke and chaos right after the blast - is it possible to use that to sneak through the doors without being spotted?
I tried it, but have had no luck so far and I'm quite sure that I'm not being spotted anywhere else. I've also tried to hide in containers and dark spots around the room right after the blast (to wait until they get calm again), but guards are always aware of my location anyways.