The Man Who Talked Too Much (1940) George Brent, Virginia Bruce, Brenda Marshall
The Projection Room
It took me until the stunt with the poison to realise I`d seen this plot before- not once but twice before. It is a version of the 1932 `The Mouthpiece` starring Warren William & the lovely Sidney Fox. It was remade again as `Illegal` in 1955 starring Edward G Robinson. Both of those other versions are on this site.