Germ warfare, one of the most insidious forms of killing known to man, was banned by civilized nations before World War II. But behind the treaties and international agreements, the experimental work, the building of bombs and shells filled with diseases such as tetanus, anthrax an plague went on. In this documentary, Peter Williams tells for the first time the story of a secret branch of the Japanese Imperial Army, UNIT 731. He reveals that the Japanese tested their weapons on thousand of prisoners-of-war – and that British, Australians and Americans were among those experimented upon. He sets out to find the scientist responsible and unearth a secret dealt hat, at the end of the war, protected these scientist from prosecution as war criminals. And he talks to some of the prisoners-of-war in both Britain and America, who survived the attentions o the men of UNIT 731.