A blond girl caught watching a couple having sex is harshly spanked and whipped. She gets revenge by having the brunette bound and whipped, then she has wild sex with the guy. However, the girls make up in the end via a strap-on session. With what is shown you can read between the lines.
The film is in the public domain, and was re-released as part of the Cult Epics compilation DVD Vintage Erotica Anno 1940.