In 1946, Mr. Wilson (Edward G. Robinson) of the United Nations War Crimes Commission is hunting for Nazi fugitive Franz Kindler (Orson Welles). Kindler has effectively concealed his Nazi activities prior to his escape to the United States. He assumes a new identity, Charles Rankin, lands a job as a university professor and marries Mary Longstreet (Loretta Young), who is the daughter of Supreme Court justice Judge Adam Longstreet.
Wilson releases Kindler’s former associate Meinike (Konstantin Shayne) and follows him to Harper, Connecticut, but Meinike is strangled before he can identify Kindler. Wilson must convince Mrs. Rankin, the only person who knows for certain that Meinike came to meet her husband, that her Charles is a war criminal.