Adam Bede is a young workman of twenty-six in the town of Hayslope in Loamshire. He is the foreman of a carpentry shop where his brother, Seth, also works. The novel opens in the workshop with an argument among the men about religion. We learn that Dinah Morris, a Methodist preacher with whom Seth is in love, will speak in the village that evening.
Seth goes to the prayer meeting and afterwards proposes to Dinah, who refuses him. Meanwhile, Adam has gone home and found out from his mother, Lisbeth, that his father, Thias, has gone off drinking instead of finishing a coffin he had contracted for. Working all night, Adam finishes the coffin, and he and Seth deliver it in the morning. On their way home, they find the drowned body of their father in a brook.
Joshua Rann, the parish clerk, informs Mr. Irwine, the local Anglican clergyman, that the Methodists are stirring up dissension in Hayslope. Mr. Irwine and Arthur Donnithorne, grandson and heir of the local landowner, ride over to see Dinah at the Hall Farm, a place tenanted by the Poysers, Dinah's uncle and aunt. Mr. Irwine speaks to Dinah and is impressed by her religious sincerity. Meanwhile, Arthur flirts with another of the Poysers' nieces, Hetty Sorrel, and she is greatly flattered by his attentions.
Mr. Irwine informs Dinah of Thias Bede's death, and she goes to the Bedes' cottage and comforts Lisbeth. Arthur learns on the same occasion that Hetty will be at the Chase, his manor, in two days' time, and he places himself so as to meet her in a grove on the grounds. After talking with her, he is ashamed of himself for being attracted to a mere farm girl, but he cannot break the spell and later that day intercepts her again in the same grove and kisses her. Ashamed of his behavior once more, he decides to tell his troubles to Mr. Irwine, hoping that confession will cure his passion. But when he speaks to the clergyman at Broxton parsonage the following morning, he loses his nerve and says nothing about Hetty. Meanwhile, Dinah has encouraged Hetty to come to her if she ever needs help, but Hetty, a thoughtless little thing who feels that no trouble will ever come to her, repulses the offer. Dinah leaves for her home in Snowfield, Stonyshire, the next day.
Thias Bede is buried, and Adam reflects that now he can begin to look forward to marriage; he is in love with Hetty. He goes to the Hall Farm and finds that Hetty seems more friendly towards him than in the past; he doesn't realize that her thoughts are all of Arthur, and his hopes rise. While visiting Bartle Massey, the local schoolmaster, that evening, he learns that the keeper of the Chase woods has had a stroke and that the job may be offered to him. Adam's marriage prospects look bright indeed, both from a financial and an emotional viewpoint.
Arthur's twenty-first birthday arrives, and all the tenants of the estate gather for a grand celebration. There is a round of toasts at dinnertime and everyone wishes the popular Arthur well. Adam is offered the job as keeper of the woods and he accepts it. There are games in which the townspeople compete in the afternoon and a dance in the evening. At the dance, Adam discovers by accident that Hetty is wearing a locket which looks like a lover's token, but he dismisses the thought that she is interested in another man. The locket, of course, is a gift from Arthur; he and Hetty are carrying on a secret affair.
About three weeks later, Adam happens to be passing through the grove on the Chase grounds when he finds Arthur and Hetty in an embrace. He is furious, starts a fight with Arthur, and knocks him out. When Arthur revives, Adam forces him to promise to write a note to Hetty breaking off the relationship. After much soul-searching, Arthur composes the note and gives it to Adam to deliver. He then leaves to join his regiment in the south of England. Adam delivers the note, trying to soften the blow to Hetty as much as possible. Before she reads the letter, Hetty refuses to believe that Arthur wants to break off the relationship; she is convinced that Arthur will marry her. After she reads it, she is in despair. She wants to leave home and go into service as a maid, but the Poysers won't let her. Finally she begins to feel that marrying Adam wouldn't be such a bad idea after all. Meanwhile, Dinah has written a friendly letter to Seth from Snowfield, and Mrs. Poyser has verbally routed Squire Donnithorne, Arthur's grandfather, who was bent on making a sharp deal with respect to the Poyser's farm.
When Adam notices that Hetty's friendly attitude toward him does not change, he concludes that there had really been nothing serious between Arthur and her. He proposes to her, she accepts, and the wedding is set for the following spring. Adam is deliriously happy and spends the next three months making preparations. Hetty, meanwhile, has fits of depression and contemplates suicide; she is pregnant by Arthur. She decides to run away and go to Arthur; telling the Poysers that she is going to visit Dinah in Snowfield for a week or two, she sets out.
After traveling for seven days, Hetty arrives sick, exhausted, and penniless, at Windsor. Here she is befriended by an innkeeper and his wife who inform her that Arthur's regiment has left for Ireland. Hetty faints in despair, but the next day her courage revives, she gets some money from the innkeeper in exchange for the jewelry Arthur had given her, and she heads back north, intending to go to Dinah in Snowfield. After five days of traveling, though, her spirits give out, and she leaves her coach and wanders out into the open fields. She spends part of a night by a pond but can't summon the courage to kill herself and so resumes her journey on foot towards Stonyshire.
When Hetty does not return in the expected time, Adam decides to go to Snowfield and bring her back. He discovers, of course, that she has never been there, and he tries to trace her but to no avail. Realizing that she has probably gone to Arthur, he resolves to go to Ireland. He stops at the parsonage to tell Mr. Irwine his plans and is shocked to learn that Hetty is in prison in Stoniton for the murder of her baby. He and Mr. Irwine go to Stoniton; Mr. Irwine returns the next day to break the bad news to the Poysers, while Adam rents a room and stays. Meanwhile, Arthur's grandfather has died and Arthur has set out for home from Ireland.
As the trial begins, Adam sits in his room in despair. Mr. Irwine and Bartle Massey (who has come to stay with Adam) bring news of how the trial is progressing; Hetty's guilt seems certain, though Adam refuses to believe it. Finally he goes to the courtroom himself. Two witnesses give evidence against Hetty, the jury returns the verdict of guilty, and the judge pronounces the death sentence. Meanwhile, Arthur has returned home, found a note from Mr. Irwine explaining the situation, and left for Stoniton.
On the evening after the trial, Dinah comes to the prison and gains admittance; she has been away and has just returned to the area. She gets Hetty to confess her guilt, which the girl had refused to do before, and induces her to pray. Dinah then goes and asks Adam to come and see Hetty before she dies. He comes the following morning, the day of the execution, and gives Hetty the forgiveness she asks for. Then Hetty is taken away to the place of execution. But at the last instant, Arthur comes riding up with a reprieve; Hetty's sentence has been commuted to "transportation" (exile). The next day, Adam and Arthur meet by chance in the grove where they had fought. Arthur is repentant and plans on going off to the wars. He asks Adam's forgiveness, and Adam, after a short struggle with his pride, agrees to shake hands.
Eighteen months later, Adam visits the Hall Farm to ask Dinah, who is visiting her relatives again, to come and comfort his ailing mother. Dinah goes back to the cottage with him and stays overnight to help Lisbeth. She blushes when Adam speaks to her. After she leaves, Lisbeth tells Adam that Dinah loves him; Adam is taken by surprise, but when he thinks about it he realizes that he loves her too. That afternoon he goes to the Hall Farm and proposes; Dinah wants to say yes, but her sense of duty stops her. She says she will return to her work among the poor and think about it. Adam reluctantly agrees and Dinah leaves. It is harvest time at the farm, and the harvest supper takes place with great gaiety.
After a month or so, Adam becomes anxious to know Dinah's decision and goes to Snowfield. He meets her atop a hill and she accepts his proposal. After another month has passed, they are married amid great rejoicing.
Some years later, Dinah and Seth are at home with Dinah's two children. Adam comes home; he has been to see Arthur, who has been away all this time and has returned a changed man. We learn that Hetty is dead, and then the novel ends on a note of domestic contentment.