In the 1830's in northern England, Riah Millican, a widow with three children, takes a job as housekeeper to a reclusive former teacher, Percival Miller. Miller makes Riah the gift of a black velvet gown, and even educates her children. But when Riah discovers the reason behind Miller's gifts, she vows to leave his house, but Miller has a hold on her, even after his death, when he leaves his house to her on the condition that she never marry. Riah's daughter, Biddy, grows up and becomes a laundress in a large house where her education keeps her from fitting in and makes her a target. But it also catches the eye of a son of the house, and with Miller's legacies, Biddy may yet find her way to happiness.
When the ailing husband of an adulterous wife is discovered bludgeoned to death and suspicions fall on the older woman's young lover, the newly widowed woman claims that it was she who was solely responsible for the death despite evidence that points to the contrary in this dramatic account of true-life 1935 trial that shocked all of England. Though notable evidence and strong suspicion suggests that the murder may have been of crime of passion perpetrated by the jealous lover only half her age, Alma Rattenbury (Helen Mirren) confesses to the murder of her husband and is soon brought to trial. Despite the fact that Alma is already being deemed guilty by the general public for her adulterous indiscretion alone, her lawyer, star attorney T.J. O'Connor (David Suchet), remains convinced that his client will eventually be cleared of all charges.