Based on Vonnegut's novel, Mother Night is the ironic story of Howard W. Campbell is an American-born playwright who has made his life in pre-war Germany. He is a devoted husband to his wife and famous German actress, Helga. He's a romantic and more concerned with good over evil than anything political. One day an American agent, after appealing to Howard's sense of heroics, recruits him as a spy for America. This will change his life for the worst. This is an example of why they say hindsight is always better than foresight.
Campbell will use his powerful way with words and his celebrity position to present Nazi propaganda on a radio show. He would write speeches to be reviewed. They would come back with editing marks all over. Without knowing how this worked, these marks indicated to him where to make pauses, throat clearings, or coughs to pass this secret information to the allied forces. He begins to get a little too good at his job. He realizes this as well, as he later states, "You become what you pretend to be." Later in the movie, his father-in-law even tells him he learned how to be a Nazi by listening to his show. This unwelcome publicity causes Campbell a dilemma. Which side was he really on? Was he an American who inadvertently helped the Nazis? Or was he an American not reluctant to help the Nazis? Perhaps, he was just a Nazi posing as an American? .
As the war proceeds, the only thing that makes any sense to him is his "Nation of Two." This is the relationship between him and his wife. To him, it is the only thing that matters and is beautiful. However, this will soon change. He's sitting at his typewriter, preparing his next speech when he is told that his wife has died at the arms of the Russians. After this his whole life begins crashing at an incredible rate. .
He decides to get away from everything and travel the German-countryside until the war passes. Two months into it he is captured by an American soldier who recognizes his voice from the airways but unaware of what his part really was.