BEWARE... scary spoilers below... here are the things I learned from Paranormal Activity 2:
Demons don't much like pool cleaning equipment.
The 15th time you cut to a static shot of a doorway, something is just bound to happen.
When trying to win back the first born male child of a couple who benefited from a deal with the devil, evidently the smart move is to throw the automatic pool cleaner out of the swimming pool every night for two weeks (see above) and repeatedly make a mess in the couple's kitchen.
If that doesn't work, thumping and bumping at odd hours is equally effective at communicating your dark desires.
When people don't interpret this demonic outreach properly, boy can those demons get pissy.
When you come home to find your live-in Hispanic maid trying to rid your home of evil spirits, that's not a good sign.
Evidently it is impossible for a couple to take their toddler with them when they go out to dinner.
If you have security cameras running 24/7, the last thing you want to do is check them after someone claims to have experienced a supernatural event in your home.
If you do check them, make sure you only find the supernatural events that could have a plausible real world explanation. Do not check the tapes that would show babies levitating.
Seriously, what is the deal with demons and swimming pool cleaners?
There is no business deal so important that you should leave your catatonic wife and terrified daughter alone, even if it's just for a "couple of hours."
Oh, wait. You own a string of Burger King franchises. Strike the above, of course you need to take the meeting.
You should always tidy up your basement before a supernatural onslaught. Boxes and spare bicycles are some scary shit in the dark.
