The Lady Vanishes(1979)

On the eve of World War II, zany heiress Amanda Kelly travels by train to Switzerland. While passing through Germany, she meets a sweet elderly lady, who suddenly vanishes. Distraught, she questions her fellow passengers who claim that the woman was never there. Unsure if it's all in her mind or if there's a more sinister plot afoot, Amanda teams up with photographer Robert Condon to discover the truth.