In 1952 the scientists at Porton Down were carrying out secret germ-warfare trials off the coast of Lewis in the Outer Hebrides. One of the germs they were testing was plague - the Black Death. One evening, as a trial was about to start, a trawler sailed unexpectedly into the danger zone. Rather than stop the tests, the captain of the naval ship gave the order to continue, and the germs were released into the path of the trawler. Jolyon Jenkins pieces together the events and the subsequent cover-up, using newly declassified secret documents, interviews with witnesses, and the diary of the chief scientist to shed light on a virtually unknown episode of the cold war. Producer Jolyon Jenkins