PG Wikipedia - 'The story is a thriller that revolves around the Lebanon family who live at Mark’s Priory. Lady Lebanon (Helen Haye) tells her son, Lord William Lebanon (Marius Goring) that he must marry his cousin Isla Crane (Penelope Dudley Ward) to continue the family line. However, William has no intention of marrying Isla and matters are made more complicated due to Isla falling in love with architect, Richard Ferraby (Patrick Barr), who has come to Mark’s Priory to draw up renovation plans. At the same time, the strange behavior of two footmen and the family physician (Felix Aylmer) add to the mystery surrounding the family and eventually rumour and speculation lead to a murderous conclusion.'