North by Northwest is famous for its famous action sequences such as hanging on Mount Rushmore and the crop duster plane scene.
Essentially it is a film of mistaken identity as advertising executive Roger Thornhill (Cary Grant) is mistaken for George Kaplan by some bad guys in league with a foreign power presumably Russian.
The trouble is Kaplan is a made up operative created by the CIA to flush out the film's villain, the urbane but deadly Vandamm (James Mason) and his cronies such as the fey henchman Leonard (Martin Landau) who are out to get Thornhill.
Thornhill in order to prove his innocence must evade capture from the bad guys and also the police as he is wanted by everyone. Only a beautiful blonde Eve (Eva-Marie Saint) aids him in this cross country chase but she is more than an innocent bystander as she might be in league with Vandamm.
This is an escapist action film that mixes tension with some comedy and Grant was always adept with light comedy. The film is overlong, it just feels 15 minutes too long and the villains motives seems to be rather cloudy.