Sen. Harry Truman is asked not to investigate a suspicious war plant in Washington State.
Truman was chairing a committee on possible war profiteering when this plant caught his attention. FDR’s Secretary of War, Harry Stimson, was one of the very VERY few who knew this plant was secretly involved in activities connected to the Manhattan Project. When asked to curb the investigation with no real explanation given, Truman, who was described as “a veteran and a patriot”, told Stimson to “say no more”, and the inquiry stopped.
It was only after FDR’s death and Truman became President did he find out the nature of the Manhattan Project.