They Came to Blow Up America

Because of his German parentage, government agent Carl Steelman is assigned to by his chief, Craig, to join the Nazi Bund, to obtain information on the underground activities of the group. Steelman is welcomed and becomes a trusted member of the group. His father, Julius Steelman, unaware of this son's real mission, drives him from their home. The government agents raid a Bund meeting and Steelman assumes the identity of one of the members who was about to depart to Germany for training. (imdb)