The movie I'm searching for in this instance is likely an early 1960s sci-fi/horror piece. I can only recall the final dramatic ending scene of the movie, though I think someone will quickly recognize it.
The movie is in black and white with a typical suit-wearing, problem-solving hero who has cornered the villain/monster in a precarious position. The final scene takes place on a large water tower at night. The hero is hanging from the tower's ladder while fighting with the villains, both of whom are wearing masks either intended to hide their identity or that indicate their inner nature. Its not clear to me what happened to the villains, but shortly into this scene they lost their footing and fell off of the tower. What I recall specifically about this action was that the filming was zoomed in on the masks of each figure as they fell (separately) exaggerating their features and increasing the drama. A cut to a wide angle view of the long fall of each body followed, with a close shot of each body on the ground. The hero approached the larger body and pulled off its mask indicating the identity of the mad scientist or lead villain, as the movie concluded.
I may have started viewing this movie late in the action as I cannot seem to recall much else, though I suspect the above is enough for an ID.