International Lady

International Lady is a 1941 American spy-drama film directed by Tim Whelan and starring George Brent, Ilona Massey and Basil Rathbone. 
During the production stage it was originally titled as "G-Men versus Scotland Yard". It was released shortly before the entry of the United States into World War II.
Plot.
An American operative in Great Britain (George Brent) and his counterpart from Scotland Yard (Basil Rathbone) suspect the beautiful singer Carla Nillson (Ilona Massey) of espionage. As they cleverly unravel her technique of singing in code over the radio, they track her from London, to Lisbon, to New York, where they succeed in tying her to a wealthy candy manufacturer who is, in reality, the saboteur mastermind.