Jonathan Frid's face becomes wonderfully interesting when he raises his eyebrows.
I don't think Chris had much of a future as an architect. He should have been interested right from the start in designing a place that would hold the werewolf securely during the full moon, and the mausoleum, with its secret room, should have intrigued him.
What does Chris think might be the reason there's a coffin in the secret room? It wouldn't occur to him that there might be an on-again-off-again vampire hanging around. So maybe he would wonder...did somebody want to conceal a murder? If so, then what happened to the body? Maybe it was discovered and the murder was solved in the 19th century, and now everybody has forgotten that there ever was a mystery.
Barnabas didn't expect anybody to come to the mausoleum overnight, but has he forgotten David's gift for being in the wrong place at the wrong time? Barnabas should have brought along a folding chair and a book, and spent the night making sure that nobody would release the werewolf.
We saw three Davids today. First he sort of picked on Amy, then he joined forces with Amy to creep out Mrs. Johnson, and in the end he displayed some ethical sense, drawing the line at murder. All things considered, it's surprising that David has any idea left at all of what's right and what's wrong.