It is the latter part of World War II, and all Jojo Betzler wants is to become a Nazi. He turns to his 10-year-old imagination and begins to befriend a wackier version of Nazi Germany's ruler, Adolf Hitler. One day, he finds out that his mother, Rosie, is housing a Jewish girl named Elsa. Despite going directly against his young beliefs, he has no choice but to keep quiet for his and his family's safety. Soon, he and his imaginary friend begin to see the world differently.