While the individual films may not do the greatest job of explaining things, if you step back and look at the story of the Paranormal Activity franchise as a whole, it's starting to become fairly clear: witches promised a female members of a certain bloodline to a demon who would collect the girls' first male heir as payment for... something or other.
In that sense, there is a certain amount that can be inferred from what little information was revealed in the Paranormal Activity 4 trailer, and teasers, and what little more is revealed in this new teaser seen above.
Chronologically speaking, Paranormal Activity 4 is set in 2011, five years after the events of PA 1& 2 - twenty-four years after the events of PA3 - and we now follow a young girl named Alice (Kathryn Newton) who begins to document the creepy things that have been happening in and around her house, ever since a woman and her strange little boy moved into the area.
In this teaser we see clues in a ghostly "echo" of what seems to be Demon-Katie walking away with her nephew Hunter (as seen at the end of PA2) - Hunter being around the same age in 2011 as the mysterious young "Robbie" who has been creeping Alice out. The second clue is the repeated flashing of a symbol (circle in a triangle) we saw at the end of PA3, when it was revealed that the grandmother of Katie and her sister Kristi was actually a crazy witch whose coven had sold the young girls as brides to a demon.
There's no gurantee that things of this nature don't happen in cycles, and that Demon-Katie and young Hunter (if that is indeed who Robbie really is) might not be scouting out another nubile young bride for the demonic force driving this whole franchise. We'll have to see if such a fate befalls Alice and her mother - and if we maybe get some answers about all the lingering plotholes and gaps along the way.
Paranormal Activity 4 will be in theaters on October 19, 2012.
Source: Yahoo Movies