That changes little! Take this, a barrage of blue!
The culprit was Meridith! She lured Betty into the library and knocked her out from the hidden passageway. Mr.Ward, opened the door and saw her body, so he called the police. Meridith enrered the room and shot her. Meridith wanted to kill Betty out of spite of Betty’s promiscuity in the past.
A thought occurred to me. Confirm.
The state of the room or anyone inside it was not changed between the time that Ward opened the door until the police arrived.
Now, to continue my attack.
The culprit was Sarah! She lured Betty into the library and killed her, with a gun. Sarah escaped the room using a hidden passage. The purpose of locking the door was to create an illusion of a closed room. Sarah wanted to kill Betty because she wanted to be Louis’s girlfriend.
The culprit was Ward! He lured Betty into the library and killed her, with a gun. He escaped the room using a hidden passage. He was expecting to have seen Betty’s body in the hidden passageways not in the room. The purpose of locking the door was to create an illusion of a closed room. He wanted to kill Betty because he wasn’t being paid enough, or she had been involved with him in the past and he was enraged about being set aside.