London 1862. Sue Trinder, orphaned at birth, grows up among petty thieves - fingersmiths - under the rough but loving care of Mrs Sucksby and her 'family'. But from the moment she draws breath, Sue's fate is linked to that of another orphan growing up in a gloomy mansion not too many miles away.

A grieving upper class woman becomes a "Lady Visitor" at Millbank prison, hoping to escape her troubles and be a guiding figure in the lives of the female prisoners. Of all her friendships with prisoners, she is most fascinated by Selina - a medium.