Overview:Dan Snow and Raksha Dave investigate how the plague devastated Britain 700 years ago, killing around three million people across the country. In the first edition, Dan heads to Melcombe Regis in Dorset as he traces the spread of the plague and finds out how the disease reached Britain's shores in 1348. At The Old Operating Theatre in London, Raksha witnesses the horrific symptoms of this deadly disease and the terrifying outcome for those who fell victim to it, and also investigates the recent discovery of mass graves beneath a tranquil London square.