By today's standards it seems quite dated, but back in 1950, the possibility of this happening seemed very real. The performances of the stars (Robert Ryan and Laraine Day) are solid and the supporting cast is great (especially Janis Carter and William Talman, who is wearing the craziest suit jacket I've every seen!!). The style is very film noir...close ups of faces showing over the top expression, jerky body movements, and odd, minimalist lighting techniques. Remember too, that it's 1950 and acting styles today seem far less "dramatic".
The subject matter seems paranoid, but for those of us old enough to remember the Cold War, the fear of what the "commies" were up to was VERY, VERY real. I remember "duck and cover" and "...we will bury you!". Some of us might still associate communism with the labor unions (which is the salient point of the plot). As silly as this movie will seem to younger people, try to remember from a historical perspective that it was only five years from the end of World War II, and herein were the first clashes of the two "great ideologies". At the time it was either freedom or subjugation (democracy or communism). Subtle, this movie is not...
There are better examples of film noir, but this a very good example. It's not the worst way to blow 70 plus minutes of your day and just for the historical (not hysterical) panorama, it is worth a look.
It has just recently been showing on Turner Classic Movies as "Woman on Pier 13"...that title is much better. Under either title, give it a chance and enjoy an example of a time and film style gone by.