This is a social novel written by George Eliot about political disputes in a small English town at the time of the First Reform Act of 1832.

As the story starts, the reader is introduced to the fictitious community of Treby in the English Midlands in 1832, around the time of the First Reform Act. Harold Transome, a local landowner, has returned home after a fifteen-year trading career in the Far East. Wealthy from trade, he stands for election to Parliament from the county seat of North Loamshire. But contrary to his family's Tory traditions, he intends to stand as a Radical. This alienates him from his traditional allies and causes despair for his mother, Mrs. Transome. Harold Transome gains the support of his Tory uncle, the Rector of Little Treby, and enlists the help of his family lawyer, Matthew Jermyn, as an electioneering agent.

Much of his electioneering is focused in Treby Magna. In this village resides Felix Holt, who has recently returned from extensive travels in Glasgow to live with his mother. He meets with Rev. Rufus Lyon, a Dissenting minister in Treby Magna, and his stepdaughter, Esther. Felix and Mr. Lyon become ready friends, but he appears to treat Esther with condescension. Felix and Rev. Lyon both appear aligned to the Radical cause.

Harold Transome learns that Jermyn has been mismanaging the Transome estate and embezzling money for himself. Transome remains silent during the election, yet Jermyn tries to devise a plan to save himself from future prosecution. Meanwhile, Felix witnesses some electioneering for the Radical cause in the nearby mining town of Sproxton. He is upset with the 'treating' of workers with beer in exchange for their vocal support. Felix relays his concerns to Harold Transome, who chastises John Johnson for his electioneering methods. However, Jermyn convinces Transome not to interfere.

Rev. Lyon learns from Maurice Christian, servant of Philip Debarry, about the possible identity of Esther's biological father. Rev. Lyon decides to tell Esther the truth about her father. Esther's outlook on life changes upon finding that she is in fact Rev. Lyon's stepdaughter. Her relationship with her stepfather deepens, while she also desires to emulate the high moral standards impressed upon her by Felix Holt. Seeing the change in Esther's character, Felix Holt begins to fall in love with her. However, both share the feeling that they are destined never to marry each other. Meanwhile, Rev. Lyon challenges Rev. Augustus Debarry to a theological debate. The debate is initially agreed to, but is cancelled at the last minute.

Riots erupt on election day in Treby Magna. Drunken mine workers from Sproxton assault townspeople and wantonly destroy property. Felix Holt is caught up in the riots, and tries foolhardily to direct its hostility away from the town. But in the end, Felix Holt is charged with the manslaughter of a constable who tried to break up the riot. Harold Transome also loses the election to Debarry.

Harold Transome begins legal proceedings against Jermyn for the latter's mismanagement of the Transome estate. Jermyn counters by threatening to publicise the true owner of the Transome estate. However, Maurice Christian informs the Transomes that the true owner of the estate is in fact Esther Lyon. Harold Transome invites her to the Transome estate, hoping to persuade her to marry him. Harold and Esther establish a good rapport, and Esther also becomes more sympathetic with Mrs. Transome, whose despair has continued to deepen. Esther feels torn between Harold Transome and Felix Holt. She compares a life of comfortable wealth with Harold Transome and motherly affection with Mrs. Transome, to a life of personal growth in poverty with Felix Holt. Meanwhile at Felix Holt's trial, Rev. Lyon, Harold Transome and Esther Lyon all vouch for his character, but he is nevertheless found guilty of manslaughter. However, Harold Transome and the Debarrys manage to have Felix Holt pardoned.

Harold Transome proposes to Esther Lyon, with the eager support of Mrs. Transome. But despite Esther's feelings towards both Harold and Mrs. Transome, she declines the proposal. In an altercation between Jermyn and Harold Transome, it is revealed that Jermyn is Harold Transome's father. Harold considers he will no longer be suitable for marriage to Esther. Esther also surrenders her claim to the Transome estate. The story ends with Felix Holt and Esther Lyon marrying and moving away from Treby, along with Rev. Lyon. Matthew Jermyn is eventually ruined and moves abroad, while John Johnson remains and prospers as a lawyer. The Debarrys remain friends with the Transomes, and the contest to the Transome estate, while widely known, is never discussed.