Further investigation led the police to the conclusion that Betty wasn’t shot.
I refuse. After Ward opened the door, many guests entered the library, and even a doctor amongst them confirmed Betty’s death.
Indeed there are hidden passages in the library, however the culprit never used a hidden passage to enter or leave the library. Ghosts can pass through walls, isn’t that common sense?
Ward knew nothing about hidden passages, he just speculated there might have been one because he knew the door couldn’t be locked from the outside, yet all he could see was Betty’s body.