In order to help bring Nazis to justice, U.S. government agent T.R. Devlin (Cary Grant) recruits Alicia Huberman (Ingrid Bergman), the American daughter of a convicted German war criminal, as a spy. As they begin to fall for one another, Alicia is instructed to win the affections of Alexander Sebastian (Claude Rains), a Nazi hiding out in Brazil. When Sebastian becomes serious about his relationship with Alicia, the stakes get higher, and Devlin must watch her slip further undercover.