The attic section:

Open the door and shoot the guard in the big room. A ghost, and guards will come at you from the small rooms as you enter the main room. Fight them as they come but make it as quickly as possible into the maze of wooden barrels for the brass key. Shoot any remaining guards from here then switch to the axe for the ghost. Unless you are at 20% or lower on health avoid the water puddles when you move through the room. In any case find a full ammo clip in the secret room at the end of the passage outside the main room. Find health chalices in two of the small rooms.

Continue.