Robert Moore is a mill owner noted for apparent ruthlessness towards his employees. He has laid off many of them, and is apparently indifferent to their consequent impoverishment. In fact he had no choice, since the mill is deeply in debt. He is determined to restore his family's honour and fortune.As the novel opens Robert awaits delivery of new labour-saving machinery for the mill, which will enable him to lay off additional employees. Together with some friends he watches all night, but the machinery is destroyed by "frame-breakers" on the way to the mill. Robert's business difficulties continue, due in part to continuing labour unrest, but even more to the Napoleonic Wars and the accompanying Orders in Council, which forbid British merchants from trading in American markets.Robert is very close to his cousin Caroline Helstone, who comes to his house to be taught French by his sister, Hortense. Caroline worships Robert. Caroline's father is dead and her mother has abandoned her, leaving her to be brought up by her uncle, Rev. Helstone. To keep himself from falling in love with her Robert keeps his distance, since he cannot afford to marry for pleasure or for love.Caroline realises that Robert is growing increasingly distant and withdraws into herself. Her uncle does not sympathise with her "fancies". She has no money of her own, so she cannot leave, which is what she longs to do. She suggests that she might take up the role of governess, but her uncle dismisses the idea and assures her that she need not work for a living.Caroline recovers somewhat when she meets Shirley, an independent heiress whose parents are dead and who lives with Mrs Pryor, her former governess. Shirley is lively, cheerful, full of ideas about how to use her money and how to help people, and very interested in business. Caroline and Shirley soon become close friends. Caroline becomes convinced that Shirley and Robert will marry. Shirley likes Robert, is very interested in his work, and is concerned about him and the threats he receives from laid-off millworkers. Both good and bad former employees are depicted. Some passages show the real suffering of those who were honest workers and can no longer find good employment; other passages show how some people use losing their jobs as an excuse to get drunk, fight with their previous employers, and incite other people to violence. Shirley uses her money to help the poorest, but she is also motivated by the desire to prevent any attack on Robert.One night Rev. Helstone asks Shirley to stay with Caroline while he is away. Caroline and Shirley realise that an attack on the mill is imminent. They hear the dog barking and realise that a group of rioters has come to a halt outside the rectory. They overhear the rioters talking about entering the house, but are relieved when they decide to go on. The women go to the mill together to warn Robert, but they are too late. They witness the ensuing battle from their hiding place.