Set in German-occupied Norway, this is an embellished account of the remarkable efforts of the Norwegian resistance to sabotage the German development of the atomic bomb. Resistance fighter Knut Straud (Richard Harris) enlists the reluctant physicist Dr. Rolf Pedersen (Kirk Douglas) in an effort to destroy the German heavy water production plant near the village of Rjukan in rural Telemark. In the process, Pedersen discovers that his ex-wife Anna (Ulla Jacobsson) and her uncle (Sir Michael Redgrave) have also joined the resistance. British commandos dispatched to destroy the plant are killed when their glider hits the mountainside at night. An improvised raid by the resistance ends in the partial destruction of the heavy water canisters, but the contingency plans of Reichskommissar Terboven (Eric Porter) enable the Germans to resume production quickly. Pedersen wants to recommend to London that the Allies bomb the plant.