The Lady Vanishes (1979)

On an express train traveling through pre-World War II Germany, American heiress Amanda Kelly befriends a cute old nanny, Miss Froy. But when Miss Froy disappears, everyone Amanda questions denies having ever seen her. Eventually Amanda persuades American photographer Robert Condon to help her search the train, during which they discover that Miss Froy wasn't quite what she seemed. (IMDB measham)

The film was made and released about forty-three years after its source novel "The Wheel Spins" by Ethel Lina White had been first published in 1936. 

Second of two late 1970s remakes of Alfred Hitchcock movies from Hitch's English black-and-white 1930s talkies period, this film being a remake of 1938's The Lady Vanishes (1938). The first had been 1978's The Thirty-Nine Steps (1978) (a remake of 1935's The 39 Steps (1935)). 

Final Hammer Films for about twenty-nine years until 2008's Beyond the Rave (2008)