In Dorset, Alan unearths the story of William John Bankes, an Egyptologist who filled his family mansion with treasures while exiled abroad, but never got to see the home he lovingly created. At Corfe Castle, Oz Clarke learns about William's great, great, great grandmother Dame Mary Bankes, who resisted a three-year siege during the Civil War. Meanwhile, Joan Bakewell travels to Cambridge where the secrets of one of Kingston Lacy's paintings are uncovered using new technology.