Guess if you want to go around finding fault there's always things .. Like filmy coincidences that stretch credulity. The villains and our man Grant taking same train to Chicago allowing Saint to seduce him and send him to his death by the crop duster. And she staying in the same hotel as the mysterious Kaplan. And the needless killing of real Townsend in broad daylight when they're anyway vacating the temporary HQ. And the police that are practically blind and not able to lay their hands on Grant at the Chicago train station or toilet. Surely they're trained to get past a simple shaving cream or red cap disguise?! Guess it's another era when white men were driving taxis and working as porters.
Leave all that aside you have a great movie that rightfully belongs to a very short list of all time classics. The story just keeps moving along with no wastage of reels or frames. And keeps you engaged even if watched many times over.
Some of the humour is contrived, like the question about why Grant's previous wives divorce him. That's when they are both hanging by a thread for their lives. But most of it is top class, subtle and weaved into the main script skillfully. My favourite is where you are left to imagine what the mother says on the phone.."I didn't believe it either".
The best acting in this movie is not by Grant or Mason, is by Jessie Landis who plays the mother. Shows you good talent dont need lots of dialogue or even screen time, to impress in a film. Most actors do fantastic job, even the clerk at the train ticket counter, as well as the "Professor". But I somehow imagined Arthur Collins from the Perry Mason series playing that role. Eva Saint is somehow not as good as often reviewed. Seems as though she's speaking with some artificial accent or diction or a bit theatrical. But when she doesn't speak much, she performs great. Like the auction scene.
Hitchcock's director touch and clever photography is visible in lots of places. Especially the scene where he gradually retreats after the plane crash to steal a vehicle.
Along with Day of the jackal, this must be movie that's so perfect it's hard to improve upon. Everything precise, not a minute wasted and each frame is perfect from camera to dialogue to acting.
Watch it. There can be no spoilers for such movies. You can enjoy them time and again.