Mistress of Greyladies

WWI. Greyladies - an ancient Wiltshire manor house - is requisitioned for a hospital. Its mistress, Harriet, Joseph and their sons are allowed to stay in part of the house, but when tragedy strikes Joseph's brothers, his future at Greyladies is at risk. Latimer family legend says a new mistress of the house will be found, yet how does this happen?