This gore-fest is so tongue in cheek that it leaves a disfiguring mark on its own credibility; it sends up horror movies not out of affection, but as an excuse to pile up special effects. Sorority sisters and frat boys go where angels fear to tread when they play a prank at a long-abandoned convent. The site comes complete with its own urban legend: 40 years ago its walls witnessed the slaying of a priest and several nuns by a vengeful unwed mother, Christine, who was said to have been kidnapped and forced to undergo an abortion performed by these religious figures. Now a recluse, Christine lives in a decrepit house near the convent. As the teens prepare to paint the...