During the Nazi occupation of Czechoslovakia, surgeon Dr. Franticek Svoboda (Brian Donlevy), a Czech patriot, assassinates the brutal "Hangman of Europe", Reichsprotektor Reinhard Heydrich (Hans Heinrich von Twardowski), and is wounded in the process. In his attempt to escape, he is helped by history professor Stephen Novotny (Walter Brennan) and his daughter Mascha (Anna Lee).