Some mean kids play a mean prank on a nerdy classmate. It goes horribly wrong. The kid ends up in an insane asylum.

Ten years later, all the kids involved in the prank, now adults, are invited to a reunion at their old school. But they find it derelict and abandonded, and nobody can seem to figure out who sent the invitations...

Since there's a huge storm and they can't really leave (convenient), they break in and find the gym all set up for the reunion party. Exellent! But then they start getting picked off one by one. Bogus!