On the eve of World War II, the German Kurt Müller, his American-born wife Sara, and their three children, having lived in Europe for years, visit Sara's wealthy mother near Washington, DC. Kurt secretly works for the anti-Nazi resistance. A visiting Romanian count, becoming aware of this, seeks to blackmail him.

Not even the joys of parenthood can stop married sleuths Nick and Nora Charles from investigating a murder on a Long Island estate.