About the first half of this film looks like just another porn/slasher with no focus. There are about four sets of characters who spend time either glaring at each other or getting nude and sweaty. There are nude and sex scenes by bucketload, some of which are pretty good.
But things start to clarify into a consistent storyline, when one of the characters becomes pregnant, the blackmail plot is exposed and revenge is sought.
Columbo it certainly ain't ! But nevertheless, there are far worse porn cheapies than this one, especially one with no known stars. (The biggest star is Fan Oi Git, whom I can trace to only two other films).