You can't expect a lot from B movie series that were made to fill Saturday afternoons until it was time to show the A pic again. Which is good, because there isn't much here.
Except for a bizarre piece of science fiction called the Inertia Projector, that looks as if it were lifted directly from another Saturday afternoon serial, the Flash Gordon series. This thing shoots a light ray that is supposed to paralyze any sort of mechanical contraption. When it appears in the otherwise very realistic movie, it really seems to come from out - way out - in left field.
Others have joked about this being a precursor to the wacky Star Wars defense system that was proposed during the Reagan administration.
What I found more interesting is that this movie played into the real fear of enemy sabotage in this country a full year before Pearl Harbor.
There's no point in examining this movie too closely. Such movies were produced quickly and not designed to withstand close scrutiny. It was very much a product of its time, and while certainly not a great example of movie-making, decently done for what it was.