Abigail is a maidservant in Greave Hall, an elegant London household governed by the tyrannical housekeeper, Mrs Cotton. Whilst the widowed master slips slowly into madness, Mrs Cotton gradually usurps the position of gentlewoman of the house. She wears his dead wife's jewellery and clothes, entertains guests as though the house is her own and reserves her most despotic treatment for Abi. In the dead of night, Abi makes a desperate bid for freedom, but is soon captured and returned to Greave Hall. As Mrs Cotton's malice intensifies, a ghostly presence distracts Abi with clues to a deadly secret. And Abi now realises that she can trust no one in the house.