After 18 years in Europe Sara and Karl Müller return to Washington DC. WWII is about to start. The Müllers stay at the home of Sarah's wealthy mother Fanny Fannelly, who lives in her own world of society get-togethers and without the slighest interest in politics. Also staying with Fanny is Rumanian aristocrat Teck de Branovis and his American wife Marthe. To protect his family, Muller keeps his "underground" activities a secret from Fanny and her guests, but de Branovis is suspicious of the mild-mannered visitor. It turns out that de Branovis is actually a Nazi sympathizer, willing to betray Muller for a price. From friends at the German Embassy he finds out that Kurt is working with an anti-Nazi underground group in Germany. Using blackmail as one of his weapons, de Branovis threatens to destroy all that Muller has been fighting for. To prevent this, Muller kills de Branovis in cold blood. Now technically a murderer, Muller bids his family a reluctant goodbye, heading back to Europe to continue his vital work. When Sarah hears no more of Kurt, she knows that her oldest son Joshua will soon leave to work in the underground.