Miss Marjoribanks by Margaret Oliphant opens with the death of Lucilla's mother, Mrs. Marjoribanks, who dies after a long illness. Lucilla imagines she will be a hero when she comes home to comfort her grieving father. Lucilla plans to come home and fall in his father's arms, crying. However, when Lucilla gets home, her father, Dr. Marjoribanks, tells her he does not need emotional support because he is okay. Instead, Dr. Marjoribanks sends Lucilla back to college and tells her to concentrate on her studies. After finishing college, Lucilla embarks on a global Grand Tour in preparation for revolutionizing her hometown of Carlingford. Lucilla is interested in politics and wants to use her forums to educate the locals on how they can demand their rights after voting for leaders to represent them.
Returning from the Grand Tour, Lucilla starts a forum called "Thursday Evenings." Lucilla meets people of all ages to enlighten them of their rights. Meanwhile, Tom confesses his love for Lucilla. However, Lucilla turns down the offer and tells Tom she will not get married for the next ten years. The narrative shifts ten years later to the politics of the local constituency. The current sitting Member of Parliament has died, and people are preparing to elect a new MP. Chiltern, one of the aspiring aspirants for the position of MP, approaches Lucilla for an alliance because he notes that they share similar political ideologies. Lucilla takes her time to understand Mr. Chiltern's manifesto, and she notices that it aligns with her aspirations and expectations for the people of Carlingford. Mr. Chiltern and Lucilla organize weekly gatherings to educate people on the leaders they should elect.
Mr. Cavendish is another MP aspirant who always attends Lucilla's events. However, Mr. Cavendish is a womanizer and an opportunist who wants to lure Lucilla to marry him and support his bid for parliament. Fortunately, Lucilla discovers Mr. Cavendish's selfish interests and rejects his proposal. Lucilla continues to champion for Chiltern to become the next Member of Parliament. Before elections, the narrative shifts to Barbara and her sister Rose. Rose and her sister participate in the Thursday evening gatherings, and their role is decorating the meeting venues. Barbara secretly flirts with Cavendish, wondering why Lucilla rejected his marriage proposal.
After the elections, Mr. Chiltern emerges as the winner with a big margin, making him the new MP for the constituency of Carlingford. Lucilla feels excited because a man who understands the people's needs has taken the leadership mantle. Mr. Cavendish blames Lucilla for losing the parliamentary race because she decided to support his opponent.
The novel concludes with Lucilla joining her father, Dr. Marjoribanks and the rest of the family members to reflect on the outcome of elections and other family issues. Tom returns and insists he still loves Lucilla and wants to marry her. Lucilla, this time, accepts Tom's proposal. Lucilla asks Tom to buy her father a large estate if he is serious with the proposal. Tom agrees and buys Lucilla and her father a big estate where she lives for the rest of her life. Throughout the rest of her life, Lucilla changes her community by promoting education and eliminating poverty to empower the locals.
