The Lady Vanishes has it all. Like most Hitchcock films (especially the 30s ones), Lady finds the right balance between holiday hijinx, screwball romance, international espionage, and all-out action.
Lady starts at an inn, in a small and forgettable town in the middle of Europe. The inn is overcrowded due to a train being delayed there by inclement weather. One could be forgiven for assuming that this is a charming comedy as our cast of characters is introduced.
All is fun and games until we're shown a single startlingly shocking shot of a singer being strangled.
Nevertheless, the dominant pleasant tone more of less continues as the long-awaited train arrives in the morning. By this point we've identified our protagonist, the young and privileged Iris, who is returning home from one of a string of vacations. Her intent in returning home is to settle down in marriage with a young man as rich and spoiled and loveless as herself. We've also been introduced to the elderly Miss Froy, a kindly Governess on her way back to England after working abroad as a Governess for several years.
As everyone prepares to board the train, it's easy to forget about that brief image of murder that we've seen. That is, until a flower pot shoved out a window, intended for Froy(!), hits Iris on the head and nearly knocks her out.
Froy takes care of Iris on the train. After having tea together, the two return to their train car and Iris sleeps off the effects of her near-concussion. When she wakes up, Miss Froy is gone. Worse, the passengers in her car deny ever having seen her. Not a single passenger on the train will confirm that there was ever anyone matching Miss Froy's description on the train. Iris's panic and frustration is palpable now.
These feelings of disorientation and despair as the world is turned upside down are preoccupations of Hitchcock. Hitchcock is so excellent at detailing this modern anxiety, both visually and thematically. He does so without resorting to mopey introspection, but uses the tropes of the suspense genre to externalize emotion and display it relentlessly moving forward just as the train in Lady chugs along, in which stopping does not necessarily mean rest. Stopping the train (the momentum of the plot) is a means of highlighting decisive moments. As in the best Westerns, indeed as in the best movies, ACTIONS reveal character.
Lady Vanishes is never preachy, but it is indubitably morally instructive. Heroism and sacrifice are quietly lauded in a reserved and peculiarly English sort of way.
And the ending? I suppose it's a bit of a spoiler to mention it. The ending is delightful. There is something so satisfyingly right about it that my heart wells up with syrupy sweetness, knowing down deep that everything is and shall be good and right in the world.