"Tonight you will take the first step along a dark road from which there is no turning back. You will have to go on and on, from one madness to another, leaving behind you a wilderness of misery and hatred, until at last you are lost and destroyed".

It's an early quote in the documentary Garbo, the Spy. It's a character responding to a portly Germen General prior to the invasion of Poland. It's a warning to fascists about what inevitably lies ahead for them along their natural path.

There are a few movies credited at the end, but none of them have this quote available online for specific citation. This leads me to consider that someone on the film crew that assembled this documentary remembered this movie quote from its original airing during the war years, as the potential cited movies are mostly 1939-1942, from what I can tell.