Something's wrong - very wrong...
And in fact that fits nicely into my new* reading of the film as a (bad) dream. It's frequently illogical and bewildering, but when you start thinking 'Well why doesn't he just..?' that's because it follows the straightforward illogic of a dream. (Ernest Lehman the writer.)
That's especially so in the crazy, surreal ending, played out against giant stone faces:
The last fifteen minutes are especially (silent) cinematic, e.g. the way Grant is spying on Mason and Landau is all from his point of view, then suddenly we move inside the room. The way Hitch shoots those POV shots of Grant on the landing looking down into the room below is perhaps a foreshadowing of the vertiginous finale (and leftover of Vertigo).
Jessie Royce Landis and James Mason play their lines deliciously.
There's also a hint of Notorious going on here too (undercover woman in nest of spies).
In the drunk drive scene I seem to remember that the police car siren works really well with the score.
We think we counted 57 different camera set-ups in the crop dusting scene ('Prairie Stop, Highway 41'), beginning with one from on high that isn't repeated. I started to wonder if the whole scene could have been done in that one shot. I mean, yes it could. It would have been very cool, actually, like a Kiarostami.
That's a great (early British Hitch) touch of the Pullman conductor who's had his uniform 'stolen', then counting his money - though as Q points out he doesn't look tall enough for Grant... but there you go, there's your illogic of dreams again!
It's brilliant, by the way.
*Ed. Not quite 'new', in fact it's how you described it last time.