Character mistake: The title card shown after Deborah's suicide states that Michael's escape from the asylum takes place "Fifteen Years Later." Yet the night after the escape, Sheriff Brackett refers to her suicide having been seventeen years ago. (00:38:40 - 01:29:00)
Continuity mistake: Michael goes to his last meeting with Loomis bare faced and wearing a robe. Then he's sitting there not wearing the robe and wearing a mask.
Continuity mistake: Michael runs at Laurie and they both land on the ground. All the way down, Michael is on top of Laurie. Next shot shows Laurie on top of Michael. (01:53:45)
Answer: He was hoping that Laurie would realise that she's really his sister. However, because Laurie was just a baby and raised by another family, she had no idea why Michael was showing her the picture or what it had to do with her.