He's approached one day by an operative of the US, Major Frank Wirtanen (John Goodman) who asks him to go to work for them. Campbell declines, citing his lack of interest in politics, but Wirtanen tells him to think on it and rather than looking for a yes or no, tells him they'll look at what he does withing the Nazi party as his answer.
Campbell moves up in the Nazi ranks becoming a crucial part of the propaganda machine, giving regular broadcasts designed to turn American sympathizer to the Nazi cause and to incite hatred against the Jews and Franklin Delano Roosevelt. This position also puts him in a unique place to broadcast important information to the Allies, through a code made up of coughs, pauses and emphases that an inside man places within his speeches. Campbell has no idea what the information is himself.
His broadcasts are very effective in rallying the Nazis. Campbell tells himself he's only concerned with his life with Helga, referring to it as their "nation of two." This changes when Helga is killed while entertaining some troops. He abandons his position and travels the German countryside, stopping to see Helga's father who reveals that he always suspected Campbell was a spy but in the end decided it didn't matter, because his broadcasts served the Nazis better than anything he could have done could have helped the Allies. He's soon back to touring Germany when he's caught by the Allies, and forced to take a tour of Auschwitz so he can witness what he helped create. Wirtanen intervenes and has Campbell set up in New York City with a new name. He soon abandons his alias and nobody seems to know the difference, until he knocks on a neighbors door for help after he's cut himself. His neighbor gets him bandaged up, but his mother asks about his name. Campbell plays dumb and the mother reveals that she and her son were both at Auschwitz.
Campbell makes friends with another neighbor, a painter named George Kraft (Alan Arkin) who tells him he recognized him as part of "the brotherhood" explaining, what he means, "The Brotherhood of the Walking Wounded. It's the largest organization in the world. You don't even know it exists until you're in it. You get your membership card when you lose the one thing that gives your life any meaning, the thing that binds you together. The thing that holds the group in one piece is the fact that the members are absolutely incapable of speaking to one another." Campbell soon reveals his true past to George Kraft.
Campbell is then visited by a Neo Nazi group, who revere him, and bring with them a surprise, Helga, still alive. Campbell is overjoyed, but finds after spending a night with her, that Helga is actually Helga's younger sister, Resi, who was in love with him for years. He comes to a certain peace with that, but their reunion is interrupted by the fact that the Israelis have found him and want him for his war crimes, announcing as much on the front page of the news.
Campbell is visited by Wirtanen who informs him that George Kraft and Resi are both working for Soviet Intelligence and planning to take him to Russia. He confronts them with this knowledge and Resi swears that she wasn't going to go through with it, planning to go to Mexico instead. Campbell explains that it doesn't matter since the authorities have the place surrounded. Resi tells Campbell she's only only been living "for love." and asks him, if he doesn't love her, to give her something else to live for. When he fails to answer, she tells him she'll give him something to live for, "a woman who died for love." He watches as she takes a cyanide capsule. He's released back onto the street and realizes "I took several steps down the sidewalk when something happened. It was not guilt that froze me; I had taught myself never to feel guilt. It wasn't the fear of death; I had taught myself to think of death as a friend. It was not the thought of being unloved that froze me; I had taught myself to do without love. What froze me was the fact that I had absolutely no reason to move in any direction." He stands in the same spot for many hours until a cop convinces him to move on.
He returns to his apartment to find it ransacked and then goes to see his Jewish neighbors. He tells them he wants to turn himself over to the Israelis and thought he'd surrender himself to Auschwitzers. They help him with this and he's soon imprisoned and given three days with a typewriter to write his memoirs before his trial. He's placed in a cell within talking distance of Adolph Eichmann. He receives a letter from Wirtanen who tells him that he's bending policy to testify on Campbell's behalf, that he was acting as a spy for the Allies. This comes as little relief to Campbell, and he finally decides to settle the matter himself.
"Mother Night" is an adaptation of a novel by Kurt Vonnegut, who is largely considered unfilmable. The exception makes sense here, as "Mother Night" is as close as Vonnegut came to a conventional novel. Unlike many of his works which confront the absurdity of the world on a grand scale, he described Mother Night as "the only story of mine whose moral I know" saying, "We are what we pretend to be, so we must be careful about what we pretend to be." He also adds two more possible morals "When you're dead, you're dead." and, "Make love when you can. It's good for you."
The character of Campbell is in an interesting position to examine some of the problems inherent in World War II behavior especially among the Nazi party. Campbell himself asks Eichmann jeeringly "Were you just doing your duty?" Eichmann is not your average citizen, and has no interest in washing his hands of the holocaust, but the question is pretty well known. Campbell's situation takes it a step further, in his position, he could actually say his part in the Nazi propaganda machine was helping the Allies. Even that however, doesn't erase the very real assistance he gave the Nazis. Even if Campbell's addresses were "pretend" in his mind, they had a very real effect. His father in law, a high ranking Nazi officer tells him that it was his broadcasts that convinced him that Germany hadn't gone crazy, solidifying his commitment to the cause. Campbell is able to witness what he contributed to first hand when Allied officers give him a tour of Auschwitz. This is something that stays with him as we see when he turns himself in to his neighbors who spent time there.
Campbell knows better than to claim he was "doing his duty" for the Allies, since this doesn't erase the fact that he was doing the same thing for the Nazis. He was only in a position to help the Allies because he'd already decided not to leave Germany. As he freely admits, everything he does is in service to his "nation of two." rather than to the Axis or the Allies. Assuming a position in the Nazi party allows his lifestyle with Helga to continue as it was, attending fancy parties and having his work celebrated by all around him. The fact that he can use his position to help the Allies is a condition that just falls in his lap, so he complies. This falls in line with his estimation of himself as "not political." since he can tell himself he's in the middle of both sides. He learns though that by serving evil in order to serve good,he's still serving evil.
Eventually all of Campbell's motivations come under scrutiny, even his firmly held conviction about his "Nation of Two." We're forced to question the reality of his conviction when he accepts Resi as a version of Helga, suggesting that he was more loyal to the idea of his lover than the person herself. Once again, he simply takes what is thrown in front of him, doing the justification required to make it acceptable to himself. When he discovers that Resi is a double agent, it's too much for him to accept. Although she begs him to, he can't offer her the conviction he once espoused, that one can live for love. She gives him the last answer he would ask for and shows him, as if taking her cue from a character in his plays, "a woman who dies for love." Her action shakes up what little belief he had that his actions were passive. The inspiration from his words once again creates a very real action. This action is not to the same scale as his wartime activities, but feels as profound to him because of how personal the action is. Resi dreamed of Campbell writing a character based on her in his plays, and in a sense he did, by failing to act and allowing her to play the part.
It's no accident that Campbell is a playwright, since this gives him a larger capacity to "pretend" than most, making his living entirely on the stories he invents. He has his art as a justification for not taking a side in the war, thinking himself in service to a non political master. He also has his Helga, who is certainly intertwined with his idea of "art," serving as his muse at the very least. When Resi asks if Helga caused him to write, he corrects her assumption, saying that Helga didn't make him write, only made him write in a certain way. His capacity to pretend and his compulsion to write were there before Helga, she just lent direction.
Nick Nolte does a wonderful job of playing Campbell as a quiet, cerebral man, knowingly heading towards his own doom. Wrestling with a share of the blame in unspeakable atrocities is not something easily conveyed by outbursts In his character, we see someone who tries very hard to shelter himself from responsibility even while trying to carry the weight of what he's done. As Wirtanen points out, his plays tell us enough about his character for his story to make sense. Good and evil are important to him, and he can't act like he doesn't see them in himself forever.
Sheryl Lee carries her two roles well. Helga comes across as more an ideal than a person, and we don't really grasp her importance until she's absent. In hindsight, Campbell's loyalty to her ensures his effort to keep their life as it is. We get little sense of her character. Resi is another story, and she's far more complicated than Helga. We know that since the end of the war she became a Soviet spy. Yet, over the years she never forgot Campbell, or the envy she had over her sister's place as his muse. As with Helga, her death changes Campbell's direction, and shakes up his knowledge of what he thinks he believes. He becomes a character stripped of all motivation, and we see him very literally stopped in his tracks while everyone walks around him. When the cop tells him "Don't you think it's time to move on?" he agrees completely, knowing that as he himself wrote, he has a "full life behind him."
Alan Arkin is also very entertaining. he's a believe friend and fellow member of the "brotherhood of the walking wounded." While he's really a Soviet spy the bond he builds with Howard still rings true in many ways. They're both spies, just for different causes and governments. When his identity is revealed, he tells Howard, "This is how things are, not who I am." a sentiment Campbell may well have considered himself, when reflecting on his own career.
"Mother Night" is a bleak meditation on the moral it states, "We are who we pretend to be, so we must be careful who we pretend to be." Although on paper there is an urge to balance bad and good, to justify evil by looking for the greater good, but in this case the evil is too great to be balanced and his influence was an integral part of the darkest crimes imaginable, even if he managed to help the Allies while doing it. He could argue that he never killed anyone with his own hands, but being a successful playwright, he knew the influence that his words could have. He also had the effusive praise of the Third Reich and American neo-Nazi groups who continued to idolize him after the war. In Vonnegut's novel, Campbell tells us he's going to hang himself "not for crimes against humanity, but for crimes against himself," the one person who never really bought his pretending.