Set in German-occupied Norway, resistance fighter Knut Straud enlists the reluctant physicist Rolf Pedersen in an effort to destroy the German heavy water production plant in rural Telemark.
| Actor | Role |
|---|---|
 Kirk DouglasDr. Rolf Pedersen | Dr. Rolf Pedersen |
 Richard HarrisKnut Straud | Knut Straud |
 Ulla JacobssonAnna Pedersen | Anna Pedersen |
 Michael RedgraveUncle | Uncle |
 David WestonArne | Arne |
 Anton DiffringMajor Frick | Major Frick |
 Eric PorterTerboven | Terboven |
 Mervyn JohnsCol. Wilkinson | Col. Wilkinson |
 Jennifer HilarySigrid | Sigrid |
 Roy DotriceJensen | Jensen |
 Barry JonesProfessor Logan | Professor Logan |
 Ralph MichaelNilssen | Nilssen |
 Geoffrey KeenGeneral Bolt | General Bolt |
 Maurice DenhamDoctor | Doctor |
| WWolf FreesKnippelberg | Knippelberg |
 Robert AyresGeneral Courts | General Courts |
 Sebastian BreaksGunnar | Gunnar |
| JJohn GolightlyFreddy | Freddy |
 Alan HowardOli | Oli |
 Patrick JordanHenrik | Henrik |
 William MarloweClaus | Claus |
 Brook WilliamsEinar | Einar |
 David DaviesCaptain of "Galtesund" | Captain of "Galtesund" |
 Karl StepanekHartmuller | Hartmuller |
 Faith BrookWoman on Bus | Woman on Bus |
 Elvi HaleMrs. Sandersen | Mrs. Sandersen |
 Gerard HeinzErhardt | Erhardt |
| VVictor BeaumontGerman Sergeant | German Sergeant |
 Philo HauserBusinessman | Businessman |
 George MurcellSturmfuhrer | Sturmfuhrer |