aka Slumber Party Massacre 3, aka Stab in the Dark
How bad is it? Typical slasher sequel. Not good.
Should you see it? If 1980's slashers are your thing, it's watchable.
The first film in this series was interesting in how it subverted the genre, the second was just weird (which is not a bad thing) and this third (there was a fourth released in 2003) is true bare bones horror, executive produced by Roger Corman. The killer's given a backstory and then that's abandoned. There's volleyball at the start to up the jiggle factor. There's toplessness, mostly by Maria Ford. Hope Marie Carlton has a role. There's a vibrator electrocution, an impalement with a For Sale sign, a mallet to the head, a speargun... who has a mallet and a speargun?!... the guys who are mostly red herring jerks get offed before the girls, who eventually subdue the bad guy after blinding him.