The Lady Vanishes (1938)

This is a great adventure caper - Margaret Lockwood befriends a charming old lady - Dame May Whitty - in an hotel who subsequently disappears as they travel on a train back to England. She teams up with the pretty exasperating Michael Redgrave and together they try to find the old girl. Paul Lukas is the wonderfully understated doctor and Catherine Lacey has fun being the nun. There are also a few minor storylines running parallel with the search which add some humour and a little diversion as we discover that there are sinister forces at work. It's a simple but compelling Sidney Gilliat screenplay with Hitchcock at his suspenseful best.