Mother Night is apparently the diary of Howard W. Campbell Jr., written while he was awaiting a war crime trial in Israel. Of course Vonnegut is using the theme of a found text while claiming he only edited the manuscript. Much like the characters in his books, the authenticity of the novel itself is amorphous and unclear.
Through the course of the novel Campbell informs us that he was once a playwright turned Nazi propagandist who transmitted broadcasts espousing the Aryan philosophy across Europe. Similar to Reifenstahl’s claims, Campbell states that his own politics are nonexistent, and that he was merely doing his job. In fact, he purposefully makes these broadcasts so over-the-top that no one could possibly see them as anything but ridiculous, but in a world where people like Hitler and Himmler somehow took over an entire country, Campbell’s melodramatic broadcasts are viewed as genius. Soon he is contacted by an undercover U.S. agent who he affectionately calls his “Blue Fairy Godmother.” This agent forcibly recruit’s Campbell as a double agent, and using Campbell’s broadcasts, the Blue Fairy Godmother is able to transmit secret codes to the allied forces.
Vonnegut states in the book that the reason people are able to commit atrocities and still see themselves as a good person is the modern condition of schizophrenia. This leads to the question of whether or not Campbell is making up the Blue Fairy Godmother. Could the Blue Fairy Godmother be Campbell’s own form of schizophrenia? It's never certain whether the Blue Fairy Godmother is a real U.S. agent or a means Campbell uses to justify helping the Third Reich.
By the end of the book Campbell turns himself into the Israeli authorities so he can stand trial for war crimes. In a sense, it doesn’t really matter whether or not Campbell was a double agent because his actions had very real and harmful consequences regardless. He stoked the coals of the Nazi propaganda machine, and regardless of whether he is guilty under the law, Vonnegut uses Campbell’s own admission of guilt to show that he is morally guilty. Whether or not Campbell was a double agent he is guilty of pretending to be a Nazi sympathizer. For a post-modern novel this is a very hard edged morality tale. Oftentimes post-modernism is criticized for moral relativity (interestingly enough, those who I’ve heard use moral relativity the most are conservative historians who wish to defend historical figures who have done questionable acts, slavery being a prime example). What Vonnegut accomplishes in Mother Night is to make it clear that while the “self” is amorphous and changing, our actual actions have a clear impact on others and cannot be fortified from morality.