Japanese troops round up Chinese and Russian prisoners of war and take them to a place called Squadron 731, where they are grotesquely tortured and experimented on to test new biological weapons. Trivia: The young woman who is subjected to the lengthy and torturous experiment involving frostbite is actually director Mou's niece. She was the only person he could find willing to play the disturbing and physically demanding role which involved holding a pair of real corpse arms which were frozen for real in the subzero Manchurian temperatures.She nearly contacted frostbite herself filming it.