It's 1920, and Louisa Cannon dreams of escaping her life of poverty in London. Her salvation is a position within the Mitford household at Asthall Manor, in Oxfordshire. There she will become nursemaid, chaperone and confidante to the Mitford sisters - especially sixteen-year-old Nancy. But soon the young women find themselves entangled in a mysterious murder case.Based on a real unsolved crime and written by the author of the number one bestselling "Downton Abbey" books - first in a series.