The tape can be explained with this very simple explanation: The basement is flooded with sewer water, about three feet deep.
I discovered that by accidently stepping in it.
Here's a picture of it:
http://i25.tinypic.com/imnh5l.jpgNote the ominous smiley face-shaped dents on the wall.
Also, all of the doors have been locked. Including the one I used to get inside of the house with that's shown in the video.
Luckily, someone completely broke one of the windows in the backyard. It should be big enough for someone to fit through.
Next time I get inside, I'm doing some serious investigating.