An interesting little gem. The film begins with just enough interesting character development to keep you from hitting "eject," and you'll be glad you stuck with it.
From then on, the tension is cranked to near intolerable levels, but in the good Hitchcock way. I can't remember a film where suspense has been sustained for the entire last 3/4 of the run time. The Lady Vanishes is escapism at its finest and an experience that you won't forget.