Fairly standard Malaysian Horror.

Histeria is a valid Indonesian condition and it inflicts young girls who become possessed by the things that live behind old trees.

An all girl school.  A group of girls play a prank on a witch doctor in order to prove him a fraud but in the process they unwittingly release a demon.  During their punishment for the prank they are taken out one by one in gruesome ways, with lots of blood.

There are some interesting cultural aspects to this film, including the fact that up to a few years ago it would have been banned in Malaysia for its content.  Mostly this controversy surrounds the first lesbian kiss in Malaysian cinematic history (It wasn't much of a kiss).  

However, this film came across to me as surprisingly western and it even borrowed heavily from many western films � including The Usual Suspects.

I just narrowly recommend this one.  It's worth the watch even if you're just doing it to guess what films it borrowed from and how.