Poor Art! Given his view of 3D Movies, he's now in the position where he has been conscripted into an army of Black Hats! Imagine being reduced to the status of a footsoldier for a cause you personally despise but for which you have no choice but to fight! This is basically the situation where Art finds himself!
As Kat points out, the people in that house just seem to attract crap like this like weirdness magnets. I wonder if it's built on a dormant Hellmouth or something?