Continuity mistake: When Michael Douglas puts on his headphones to listen to the tape in his den, he puts the headphone with the cord on his left ear. When his wife startles him the cord is on his right ear.
Audio problem: There's no doorbell or buzzer sound when Michael Douglas presses the button on Alex's door. (01:41:20)
Answer: Because she is insane! And she picked the lock. By murdering the innocent pet bunny rabbit Alex was sending a message. She won't be ignored! She's just letting Dan know that she can get to him, or in this case his family (daughter's pet), anytime she wants to. He's not safe.
Alan Keddie