During the Nazi occupation of Czechoslovokia, insurgent Franticek Svoboda (Brian Donlevy) assassinates the brutal German leader Reinhard Heydrich (Hans Heinrich von Twardowski). Svoboda escapes with the aid of history professor Stephen Novotny (Walter Brennan), but Novotny is then captured, along with 400 other Czechs, through the machinations of Nazi sympathizer Emil Czaka (Gene Lockhart). The Czech prisoners are then told that if Svoboda does not surrender, they will all be executed.