Leif Tronstad assembles a sabotage group named Grouse. The aim is to assist the English commandos to blow up the water plant at Vemork. In Germany, Werner Heisenberg continues his work on the atomic reactor. Grouse is dropped over Hardangervidda and prepare a landing for the Englishmen.

Gunnerside lands on Hardangervidda and joins grouse. The twentyseventh of February, 1943, the 9 saboteurs skies down the mountain in the direction of Vemork to blow up the heavy water plant.he heavy water plant.