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.
