Plot hole: When Iris Henderson and her two friends arrive at the hotel, Iris orders dinner and asks that it be sent up to "our" room. The waiter arrives when the three are changing. But later, when it's time for bed, Iris says good night to her friends, who leave her alone in the room (as she must be for the sake of subsequent developments).
Continuity mistake: The car at the beginning of the movie stops, and one of the officers exits it to open the door to Mrs. Reardon. The movements of the policeman are in continuity between shots, but the extras on the sidewalk completely change. (00:01:00)