The Lady Vanishes
In addition to everything else he did, Hitchcock made great romantic movies. This 1938 thriller is one of my favorites. Starring Margaret Lockwood and Michael Redgrave. The obstacle: They hate each other. As she puts it, classically and memorably, "You are the most contemptible man I've ever met." With Dame May Whitty as Miss Froy, the lady who vanishes.
It Happened One Night