Don Siegel acknowledges one big mistake in his autobiography: due to a writers strike he ended up rewriting the script while he was also preparing the shoot as a Producer-Director. He should never have rushed to make this movie under such conditions. Then he puts the blame on Universal who, in the beginning, suggested he managed all three jobs, then, decided to release it as The Black Windmill, a title which bears no relevance with what the movie is about.
Sure, the storyline is far from flowing and it's a pity since there are so many fine performances in it. Donald Pleasance, John Vernon, Delphine Seyrig, Catherine Schell to name a few. Roy Budd's score is wonderfully in line with the atmosphere too. With all these, Don Siegel should really have been able to blame himself for his trademark flaw: used to shoot low budgets with lots of energy he forces a minimalistic loner hero inside the story. In his previous movie, Charley Varrick, it worked much better since the plot was more simple (aftermath of a bank robbery) with only a couple of important characters. Charley Varrick already lacked character development, but with Michael Caine, a counter-espionage civil-servant stuck between his bosses, his wife and the villains, it really bogs down the whole narrative.
It's a real pity so many things just don't add up to a tense situation. There is nice interaction in some scenes involving female characters, but basically the plot is not streamlined. One final word, Don Siegel style: the ending, as in Charley Varrick, is quite unsatisfactory. Not that it should be changed to some other outcome, but all good directors know how to close an action movie shortly after the ending climax. I don't know why Don Siegel would add some "post-coïtum" shot, having you wondering about some final twist, but no, it was just some fancy shot demonstrating how much the screenplay wasn't polished enough.
