The movie deals with the theft by German spies of the fictional "Process 97", a secret formula which, the narrator tells us, "was crucial to the development of the atomic bomb." The movie was released on September 10, 1945, only a month after the atomic bombs had been dropped on Japan, and barely a week after Japan's formal surrender. While making the film, the actors and Director Henry Hathaway did not know that the atomic bomb existed, nor that it would be incorporated as a story element in the movie. (None of the actors in the film mentioned the atomic bomb.) However, co-Director and Producer Louis De Rochemont (who produced the "March of Time" newsreel films) and Narrator Reed Hadley were involved in producing government films on the development of the atomic bomb. (Hadley was present at the final test of the bomb in Los Alamos, New Mexico, in July, 1945.) After the bomb was dropped on Hiroshima, Hadley and Screenwriter John Monks, Jr. hastily wrote some additional voice-over narration linking "Process 97" to the atomic bomb, and Rochemont inserted it into the picture in time for the film's quick release.
The scene near the beginning of the film, where a man is killed by a car, was based on a real-life incident. He was identified as Julio Lopez Lido, but really was Captain Ulrich von der Osten, a Nazi army officer in the Abwehr (German military intelligence). He was struck and killed by a cab on March 18, 1941, and his body went unclaimed for a while. The man who ran from the scene was Kurt Frederick Ludwig, known as "Joseph K.", a German agent who was eventually caught and sentenced to Alcatraz Prison. He was deported in 1953. The cab driver who hit von der Osten was a man named Sam Lichtman.
Much of the early surveillance footage of the German Embassy, and the perpetrators being lead into various buildings at the film's conclusion, is real footage of Nazi agents.
The real-life Dietrich was not a native born German-American, but a German-born naturalized citizen who was recruited by the Nazis on a return trip to Germany. The change was evidently based on an F.B.I. request.