Adam Bede follows four characters in the rural village of Hayslope in 1799. It opens with the Bede brothers, Adam and Seth, at work in a carpentry shop. The other men tease Seth about his Methodism and the fact that he is in love with Dinah, the Methodist preacher. Dinah preaches in Hayslope that night and captivates even her skeptical audience. Seth walks her home and asks her to marry him for the second time, but she refuses, saying that it will interfere with her preaching.
Adam returns home to his mother, who is worried that his father is not yet home because he has promised to make a coffin for the next day. Thias Bede used to be an honorable man who taught his sons carpentry, but he has become a drunk in the last few years. Angry with his father, Adam stays up the whole night to complete the work on the coffin. He hears a strange rapping on the door, but nobody is there.
Captain Arthur Donnithorne visits his mentor, the vicar, and tells him about Dinah's preaching. They travel together to visit the Poyser farm so that the vicar can meet Dinah. At the Poysers' farm, Mrs. Poyser's niece, Dinah, and Mr. Poyser's niece are living with their aunt and uncle. Captain Arthur Donnithorne, whose aristocratic grandfather is the Poysers' landlord, asks to see Mrs. Poyser's dairy, while Dinah impresses the vicar by explaining to him why she feels called to preach. In the dairy, Arthur flirts with Hetty and ascertains that she walks alone to his estate to learn lace-making from his housekeeper.
In the morning, Adam sets out to the village pub to find his father, but he finds him face-down, drowned in a stream. The news of the Bedes' misfortune spreads fast around the village, and Dinah visits Lisbeth Bede to comfort her. Despite the fact that she does not usually like Methodists--or any young women who she suspects could take her place in her sons' affections--Lisbeth takes to Dinah. She stays overnight with the Bedes to help Lisbeth.
Arthur intercepts Hetty in the woods on her way to his estate. He flirts with her and kisses her. After she goes home, he decides that it is not a good idea to lead her on, and he resolves not to see her in the future. That night, Hetty dreams of marrying Arthur, becoming a gentlewoman, and owning beautiful women. Dinah surprises and frightens her by knocking on her door and saying that if she is ever in trouble, she should come to Dinah.
There is a well-attended burial service in the parish for Thias Bede. Adam visits the Poysers afterward to continue his well-established courtship of Hetty. Hetty's uncle and aunt both approve highly of the match, but Adam is frustrated because he cannot tell whether Hetty loves him or not. After this visit, he attends night-school, where he is learning mathematics to improve his skill at carpentry. Bartle Massey, the schoolmaster, tells him that he would be better off to stay a bachelor.
Arthur's and Hetty's secret affair continues, and he gives her a pair of beautiful earrings and a locket. At a celebration for Arthur's twenty-first birthday, he announces that he has appointed Adam Bede the steward for his estate's forest. This appointment will finally make Adam financially viable enough to ask Hetty to marry him.
Walking through the woods a few days later, Adam is reflecting on how happy he is until he sees Arthur and Hetty kissing. Hetty runs away, and Adam confronts Arthur. The two get in a fistfight, and Adam knocks Arthur down. He makes Arthur promise to write a letter to Hetty that will end the affair. Adam personally delivers this letter to Hetty, who is devastated. The letter says, however, to call on Arthur if she is in any real trouble. Hetty tries to think of how she can get out of her situation and decides that her best move would be to marry Adam. Adam thinks that she has learned from her mistakes. They get engaged.
As the marriage approaches, Hetty grows more and more worried. She gladly accepts as a pretext to run away her uncle's idea that she should leave to fetch Dinah from where she is preaching in Snowden. She takes all of her money and follows Arthur to Windsor where he has been stationed as a soldier. It takes all of her money to arrive there, and when she is informed that Arthur's troops have been sent to Ireland, she faints away. She remembers her cousin's invitation to look to her if she is ever in trouble. Hetty sets off in the opposite direction with the resolution that if she is too cowardly to commit suicide, she will find Dinah.
Hetty's family becomes worried when she does not return after a number of days, and Adam Bede sets out in search of her. When he arrives in Hayslope, he finds that she has never visited to collect Dinah at all. Alarmed, he traces her to Stoniton. When he returns back to Hayslope, the vicar informs him that she has just been arrested for the murder of her own child.
Adam is convinced that she is innocent until he attends her trial and sees the incontrovertible proof against her. One of the witnesses is a woman in whose house she delivered the baby. Another is a workingman who saw her near the spot where she partially buried the baby in a field before it died of exposure. Hetty is sentenced to execution. Dinah visits her in prison, persuades her to confess for the first time, and gives her spiritual counseling.
Adam has sent for Arthur, who receives word first that his grandfather has died, so Arthur returns to Hayslope without knowing what has happened to Hetty. When he hears the news, he rushes to get a special pardon for her. It is delivered in the nick of time. He rides up to where Hetty is riding in the death cart accompanied by Dinah with the pardon. Hetty is re-sentenced to exile rather than death. Adam and Arthur meet again and agree to end their old argument. Arthur says that he is joining the military, and the two shake hands.
Years later, Adam visits the Poysers as they try to convince Dinah not to leave on her preaching circuit yet again. She insists that she must go because of personal temptations. When Adam says that whatever she chooses will be right, she begins to cry. He brings her home to his mother, who is ill and wanted to see Dinah again. Dinah blushes every time that Adam talks to her, and Seth and Lisbeth see that she is in love with him. Lisbeth informs her son, who, after asking his brother's permission, asks her to marry him. She refuses, saying that her first priority is religion. She leaves for Leeds to preach. After she has been gone for a few days, Adam follows her to where she is preaching. He meets her on a hill, and she admits that she has been listening to her heart and what God is trying to tell her--and that it is to marry him. The two marry, and the epilogue depicts them living happily with their entire family, including two children.