Plot hole: In the beginning, Rachel and Loomis are referring to Rachel's mother as being Jamie's step mother and Rachel refers Jamie as being her step sister. Rachel's mother is Jamie's foster mother and Jamie is Rachel's foster sister as said in Halloween 4.
Plot hole: When everyone goes back to the Myers house to set a trap for Michael, standard procedure would have the cops going through the entire house to make sure it was safe before proceeding with the plan. This would have included the attic. So how is it that they missed the corpses of Mike, Rachel, and Max the dog, as well as the shrine with the coffin and candles burning? The sequence begins with the trap set up, and later Jamie is shocked to find the corpses when she makes her way to the attic. Makes no sense whatsoever.