I'm found two of the key cards in Rockingham Castle, but I'm now stuck. I'd like to find keys for a cupboard (the only locked cupboard in the castle, from the look of it) and the key to the corridor leading up to the second floor, from the first floor on the left side of the castle.. I got further than this on my last playthrough but I can't remember how to obtain those keys or if I did at all...

How do I activate the remaining spectres? There are three (human) people I've helped, milling around the castle now. No idea what to do next. I also need to find the Emerald Key.

Never mind, I answered my own question. I'm still curious about the locked cupboard though. No progress made there.