It is 1847, northern England, and Charles Weightman has been given the unenviable task of overseeing the flooding of the Forge Valley and evicting its lingering inhabitants. Weightman is heartily resented by these locals, and he himself is increasingly unconvinced both of the wisdom of his appointment and of the integrity and motives of the company men who posted him there. He finds some solace, however, in his enigmatic neighbour, Mary Latimer. Caring for her mad sister, Mary is also an outsider, and a companionship develops between the two of them which offers them both some comfort and support in their mutual isolation.