Anti-Fascist German engineer Kurt Muller returns to the United States in 1940, with his American-born wife Sara and their three children, after spending 17 years in Europe, where Kurt has engaged in underground resistance to the rising Nazi threat. Unscrupulous Romanian count Teck de Brancovis, a houseguest of Sara's family in Washington, D.C., discovers Kurt's secret and threatens to expose his activities to his contacts at the German embassy.