Doing this out of order again, but that's what I get for having random topics.
Paranormal Activity 1 and 2 dealt with a modern family (two sisters) dealing with some form of demonic entity possessing one of the sisters and stealing the baby of the other. The third movie takes us back to when both sisters were little and living with their mom and her boyfriend in California. When one of the girls gets an imaginary friend named Toby, weird things start happening around the house. This prompts the boyfriend to set up cameras all over the house and see if he can find anything strange. The paranormal activity of the title starts to ramp up and the family looks for answers from the grandparents. Bad things happen.
This is the first narrative movie by the makers of the documentary Catfish. By placing the movie in the late 80s, there is a limit to the camera action they can have. This leads to some creative setups like a camera being set on an oscillating fan base so that it scans the kitchen. The slow, steady rhythm of the scene when something happens in the kitchen is probably my favorite moment from the whole series. You get a little bit of the Die Hard problem here (how does the same family keep thinking to document all this weird shit but do nothing about it) but it mostly works due to some strong performances.
I wouldn't start with this one but I almost would say you can end with it. Although it leaves earlier plotlines unresolved, they don't get resolved any better in the next few movies. This probably should have stopped as a trilogy.