In 1943, Karski could not return to Poland. The Government-in-Exile gave him a new assignment: To convince Hollywood to make a movie about the Polish war effort in order to sway public opinion toward a Poland threatened with Soviet domination. After the film failed to materialize, Karski went to work day and night on a book about his wartime experience. “Story of a Secret State” was published in the US by Houghton Mifflin, became an overnight sensation, selling 400,000 copies. It was quickly translated into French, Swedish, Norwegian and Icelandic.