As the first movie I have seen out of the 32-pack of "Drive-In Cult Classics" by Mill Creek, I have to admit I was pleasantly surprised. Joseph Ruben would continue directing for the next 30 years after this debut film, and it's no surprise as you can see his talent, especially when compared to a lot of the other trash that was being made at that time. Everything about this movie fits perfectly into the drive-in formula (softcore nudity/sex, etc), but it doesn't use these as a crutch, rather stands well on its own as a story. The script leaves a little something to be desired in terms of character depth, but Ruben tried to layer them, and the audience is treated to a clever twist. Definitely not a great movie, but not a terrible one and by far one of the better in the genre.
Review of The Sister in Law
