When Kenneth Holden leaves his house in his car it is early evening, but the car that chases immediately after him is shown in total darkness.When he looks back he is being pursued in early evening again, and the chase ends in total darkness.
Car #2, chasing car #1, has a split front windshield, but the closeup of the occupants shows a one piece windshield.
Claire broke off her engagement to Dr. Koster because of his heavy surgery/practice schedule, feeling he lacked time for their relationship. When her husband becomes paranoid and she consults with Dr. Koster, all of a sudden he has days free to devote to helping her, even spending nights and days at the house.