A vicious master. A cruel injustice. A secret long-held.

December 1907. Depressed by a failed examination, Vita treats a passenger injured in a train accident, a chance meeting that leads to a portrait commission for Aunt Louisa and a stay for them both at the notoriously haunted Crowswood Castle.

They find the vivacious new owner more interested in breeding fine horses than in Crowswood's gloomy traditions. The ancient castle's first renovations will be complete when a new portrait replaces that of the unhappy previous lady of the house who was banished to an asylum by her cruel husband, the Earl of Mountfitchet.

Struck down by sudden illness, Vita is confined to her room, struggling to know which of the visitors who come and go are real, and which are figments of her feverish dreams. Then workmen unearth human remains in the castle grounds and the butler confides a lifelong secret, begging for her help.

Can the old portrait help Vita untangle what happened to the mysterious lady in blue, and its connection to the Earl's disappearance? And will she escape the attentions of the strange night-visiting doctor?