The Invisible Front

The Invisible Front German Die unsichtbare Front , or A submarine spying film or Ein UBootSpionageFilm in German, is a German cloakanddaggermovie from 1932, directed by Richard Eichberg and starring Trude von Molo, Karl Ludwig Diehl, Veit Harlan and Paul Hrbiger. The story was written by Robert A. Stemmle, Curt Siodmak and Max W. Kimmich, who also presented the idea to this film to his colleagues.

Source: Wikipedia