Other mistake: In one of the first scenes in the study, Mr. Boddy hands each guest a weapon and then proceeds to turn out the lights. The room is thrown into complete darkness. Unfortunately, there is a roaring fire in the fireplace that would have illuminated the room enough for everyone to see what was going on.
Other mistake: When a gloved hand tosses an envelope's contents into the fire, most of the papers miss the fire completely.
Other mistake: In one ending, Mrs. White is responsible for Yvette's death, yet when Yvette rushes downstairs to meet her killer, Mrs. White is still heard screaming upstairs.
Other mistake: When Mrs. White enters the house, she takes off a black and white cape so she now is wearing a light coat over her dress. There is a point at which she is about to take off the coat, and with the camera angle change, she has it in her hand.
Other mistake: During the entire movie, the candles on the dinner table are lit and yet never seem to get any shorter as the movie progresses.
Other mistake: Even though it is pouring with rain, Mr. Green's coat is completely dry when he arrives at the manor. (00:07:30)
Other mistake: When everyone finds the Cop's dead body, there is a wound showing were the murderer hit him on the head with the pipe, however, the pipe shows there is no blood. (01:04:30)
Casual Person
Suggested correction: If Mrs. White was indeed the killer, she could have followed Yvette, then gone into the room where they meet before her. The screaming has stopped before Yvette actually gets inside the room.
That would be impossible. There is no way that Mrs. White could have murdered Yvette because Yvette is seen running down the stairs while Mrs. White is still heard screaming upstairs. Add to the fact that the power to the house had been shut off leaving it in complete darkness, Mrs. White had no way of seeing where she was going and would most likely keep bumping into things. Plus, when Yvette gets to the billiard room, the murderer is already inside waiting for her.
Suggested correction: Mrs. White is not screaming when Yvette is walking into the room (where she is killed) only while Yvette is running down the stairs. Yvette pauses for a brief moment to look into the dining room, then proceeds to the billiard room. There are many secret passageways in the home, and one upstairs could have led into the billiard-room.