In the bleak Norwegian midwinter of 1943, a group of resistance fighters manages to destroy machinery used by the Germans to make "heavy water", a key ingredient in building atomic bombs. The exercise, labeled Operation Grouse, was one of the most audacious raids of World War II, carried out by four handpicked commandos parachuted into German-occupied Norway. It was the plot of a Hollywood movie called The Heroes of Telemark, starring Kirk Douglas and Richard Harris, but in fact, British television presenter and survival expert Ray Mears claims the film was a pale imitation of the true story.