So after a delve into the rules glossary, I was sad that they got rid of the Hidden condition. Instead it makes you invisible, but I don't think they worded it quite right. You gain the Invisibility condition until you make noise, and enemy finds you (using the Search Action), or you attack. The requirement to be out of line of sight is only listed when you take the action, not once your invisible. Thus you could easily take the hide action outside the castle, then walk right past anyone to get inside (unless they both take the Search action and beat your roll). I doubt this was the intent, but by RAW this would be accurate. Just checking to see if I've missed something important or they did...