Marie Wallace was excellent as Jenny! I'm sure she had a ball playing crazy. I especially liked the "What color is a lie?" speech. Jenny was prone to violence, but she was a sad woman, too. It was great that so many layers were portrayed so that we, the audience, could feel sorry for her.
When Barnabas was waiting for Rachel, at first I was wondering why he waited. After all, as he said himself, he could have gone up there on his own. But then he wouldn't have been able to explain himself if he had done that.
I started thinking about the fact that today they would make DS, especially the period stories, as big grandiose romances with overpowering music, lots of gold and blue mood lighting, many edits, special effects, and a dry ice machine maybe. All that would overwhelm and beat the life out of great performances like MW's I think. It's far better just to point the camera at the actor and let her work, keep quiet, and not interfere.
I think Barnabas explained himself. If I'm right, he said that he must go to the room in the normal way, possibly leaving us to remember why, because we don't reel off exposition in our thoughts to ourselves. It would have been too easy to be discovered appearing or disappearing, or overheard talking behind the locked door, and one person for sure would be a witness, whoever the person in the Tower Room was.