This documentary is that : a documentary, so you should expect a lot of pre-war and war news reels and you do get them. One hour of them, actually. There is an acceptable commentary running the whole length of the film that tries to explain the who's who of the Gestapo. You will see many of the news reel that you have seen elsewhere, assuming you have at least a modicum of interest for that era.
The disturbing element is always the same: the gradual disappearance of any deference to the rule of law. It ends up with not even a lip service to due process. No need to even rig a trial, it would be a waste of time and the Fuhrer does not like to waste time. The turning point is probably the Rohm purge: kill first then legalize the killing the day after.
The commentator does make an effort to show the how and when of this progression but the limited time available (1 hour) put this goal a bit out of reach.
Commendably, the movie does a good overview of the Gestapo at work in most occupied territories, something I had not seen before.
The movie is also an excellent memory exerciser that will give a fresh layer on many fading memories of those archetypal villains. Yet, we see them usually beaming and the horrifying acts they committed are rarely documented with news reels, apart from very late shots on the concentration camps made by Allied reporters.
Still, it is worth to be seen.