Plot hole: When the cop comes back after making the phone call, he's just missed Norman. He heads over to the office and calls out for Bates. He's in there around 45 seconds. Then he leaves and heads towards the big house. How can Norman be at the house ready to kill him in his mothers clothes, when he had no idea the cop was back and he would not have had time to get there from where he was, right at the far end of the cabins?
Suggested correction: Because Norman heard/saw him coming up the road. Norman hesitates before he goes into a cabin or behind one, it's not clear which. He has seen Arbogast's car before and recognizes it. He goes the back way between the two buildings of cabins (just like Vera miles does later when she goes to the house) and up to the house to put the dress/wig on and be ready for Arbogast when he gets to the top of the stairs.