Fritz Lang's best work was in the early part of his career, when his imagination was able to run wild, using the magic-realist and downright surrealist tropes of expressionism to create such extraordinary visual spectacles that we felt we were in a strange anything-goes world where it didn't matter that the plot sometimes made about as much sense as Scientology.
Of course, for that approach to work, Lang needed the kind of budgets that weren't easy to come by in the difficult year of 1944. He was also still trying to adjust to the fact that expressionism had died along with silent movies, so bizarrely unrealistic sets and impossible plots would just seem quaint. This film is minor, watered-down Lang. A few of the old flourishes are still there. A pretentious doorbell so elaborate that the hero has difficulty figuring out how to use it looks like a tiny fragment of Metropolis smuggled into this movie as a souvenir, and he makes a half-hearted attempt to recreate his earlier magical use of models in a brief shot of a factory being bombed.
Lang has more success with those elements of his style where the budget doesn't matter, so most of the people we meet are memorably odd, and even some very minor characters have enough personality to make an impression. But even here, you get the impression that Lang originally hoped to take this aspect of the film a lot farther than the budget allowed. Two different lunatic asylums are mentioned but we never see a single lunatic, and a subplot about fake séances and the nutters who frequent them doesn't get as weird as we hope it's going to. And ironically, although the fact that almost everybody is slightly sinister keeps both the hero and the audience guessing as to which of them are baddies, Lang can't include one of his trademark over-the-top supervillains because it would make the identity of the Nazi master spy too obvious.
Ray Milland does a good job as a protagonist who, like most of Lang's heroes, is more confused and vulnerable than two-fisted he-men in spy thrillers usually are, though the nice girl he falls in love with is one of the film's weak points; the not-so-nice girl he's tempted by is far more interesting, and there's obviously far better chemistry between the actors. So although it's a decent enough thriller with plenty of twists and turns, it's nowhere near the best that Lang could do. And it's hard to ignore the absurdity of Nazi spies passing information they could simply hand to one another in an insanely convoluted way because the plot requires our unsuspecting hero to be given the Macguffin by mistake.
Alfred Hitchcock's 1959 masterpiece "North By Northwest" is so heavily influenced by this film that it's almost a remake, only with a vastly greater budget and a keen awareness of its own absurdity.
If any noir director was justified in adapting the tools of German expressionism to American film noir it was Fritz Lang who was a key exponent of the style In Berlin. And if there seems to be a lot of Alfred Hitchcock in Ministry of Fear, then that was because Hitch was influenced by the Germans.
Ray Milland plays a patient released from a psychiatric hospital where he had been imprisoned for the mercy killing of his wife. He wins a cake at a country fair which was supposed to have been given to a group of fifth columnists because... it contains microfilm of secret military designs! Pure MacGuffin.
Lang doesn't make the most of Graham Greene's novel. The plot survives, but its moral complexities are discarded to leave a chain of suspenseful set pieces. The script is ordinary. This is one of very few forties noirs with a contemporary WWII setting, rather than featuring the men who return but don't find the promised post war settlement.
The visual and thematic approach of the director is very noir, with the everyman trapped under the wheel of an intractable fate, pinned in the path of the tracking shots in a mesh of shadows. Lang was seriously investigated for the death his wife back in Germany in the early twenties. So maybe this felt close to home.