SLUMBER PARTY MASSACRE III: When Stalk And Slash Goes Stale
One of Roger Corman's key skills is that he knows how to squeeze the maximum amount of commercial value from any asset. However, the downside of that approach is he sometimes beats a dead horse in his attempts to get the last few cents' worth out of said asset. Case in point: Slumber Party Massacre III. After two successful entries, it was inevitable that Corman would go for a third. Unfortunately, the results have a dated, misguided feel that ends the series with a whimper instead of a buzz.
Once again, the story begins with a group of girls gathering at a house for a slumber party while one girl's parents are out of town. This time, Jackie (Keely Christian) is the nominal leader who hosts a party for her pals while pondering whether or not to move to Washington with her parents. However, such concerns are rendered moot when she and her friends find themselves under attack from an unseen killer. With the help of some party-crashing guys, they try to figure out who is attacking before it's too late. Unfortunately, the killer happens to be much more intimately involved with the group than they think...It's a boilerplate slasher-flick setup but the treatment it receives falls far below the average. The key problem is the script by Catherine Cyran. Her script undoes the film's girl-power intentions by making the heroines a dull, bubble-headed lot who are virtually indistinguishable from each other and consistently do stupid things so the filmmakers can achieve the requisite body count.
Cyran does try a few new wrinkles - having a mystery killer, developing a backstory to give said mystery killer a motive - but even those elements are muddled. For starters, the "reasons" the killer has for committing the killing spree are deployed in an incomprehensible manner (something to do with childhood abuse and sexual dysfunction). It doesn't help that the clumsy plotting makes it easy to figure out who the killer is a good reel or so before its actually revealed - and it plays out in a way that makes the other characters look like complete morons for failing to figure it out.To make matters worse, the film suffers from weak direction by Sally Mattison. With the exception of an clumsily-staged killing near the beginning, the first thirty minutes is a complete snooze. Once the killings begin, the setpieces are staged in a flat, careless style that saps any kinetic energy the film might have achieved (she also fluffs many intended jump scares). Similarly, her handing of actors is careless, 
resulting in performances that are either dull or annoyingly hammy. Her indifferent handling of the material results in a tired and joyless piece of work.In fact, Slumber Party Massacre III only has one genuinely effective scene: it occurs near the end when the killer corners one of the coeds (played by then-regular Corman actress Maria Ford) and she tries to use reverse psychology to defuse his rage. For about a minute, the film achieves tension and displays some effective acting from the underrated Ford. Unfortunately, the scene lapses into stupidity when she only makes a halfhearted attempt to escape and gets drilled to death while topless. It ends up being the tackiest scene in the entire series and accidentally portrays the kind of misogyny that the other two films are wrongly accused of (even the director is uncomfortable with this scene, which was added as a reshoot).There was never another official sequel in the series (years later, Jim Wynorski's Cheerleader Massacre would feature a character from the series and some stock footage from the first film but that's as close as anyone got to a 4th Slumber Party Massacre film). It's just as well because Slumber Party Massacre III revealed the series to be creatively exhausted. Even veteran recyclers must recognize when it's time to give up.