The narrator tells us that he met Ethan Frome while working for a power plant in rural Massachusetts. The closest town to the plant is Starksfield, and there the narrator gets a taste of life in rural New England. Frome is the most striking character in town, a tall and lame "ruin of a man," and the narrator becomes obsessed with learning Frome's story. He gathers bits of the tale from various sources around town. By chance, Frome ends up being his sleigh driver to work every morning. After about a week of riding with Frome, a terrible blizzard makes the trek all the way back to the narrator's home impossible. He is forced to take shelter at Frome's home, and there he gets the clue to Frome's tragedy. The narrator presents his vision of Frome's story to us.
We then switch to a third-person narrator and move twenty-four years into the past. Frome is a young man. Although he briefly pursued higher education in the sciences, the death of his father necessitated his return to the family farm. His mother was ill, and his cousin Zeena came to care for her. After his mother died, Ethan married Zeena out of loneliness. Zeena became more sickly and fussy as time passed, and their marriage has been loveless. But a year ago, Zeena's cousin, Mattie Silver, came to help Zeena with the housework. Ethan has fallen in love with her.
Tonight, he is fetching Mattie back from a church dance. Their walks together are some of Ethan's happiest moments, but he has never really considered acting on his feelings. On the way back, they talk affectionately to each other, and at some point Ethan puts his arm around Mattie to prevent her from falling. It is the most intimate physical contact they have ever had, and she does not push him away. Zeena is waiting up for them when they return, and the contrast between Zeena and Mattie could not be more defined.
The next day, Zeena decides to leave for Bettsbridge to see a doctor; she has been particularly ill lately. For the first time since Mattie arrived, Ethan and Mattie are going to be alone together overnight. Ethan goes about his work joyfully, and he comes home for supper to find Mattie dressed more nicely than usual. She has gone to some trouble to make the supper table look festive, and she and Ethan try to have a pleasant evening together. But Zeena is an oppressive presence even when she is absent, and the conversation between Ethan and Mattie becomes strained and awkward. Later that night, as they are sitting in front of the fire, Ethan takes hold of the piece of cloth Mattie is sewing. With her working on the other end of it, he kisses it gently. Mattie rolls up her work and makes her way to bed.
Zeena returns the next day. The doctor has told her that she has "complications," meaning that her illness is serious. She has already hired a new girl to come and help with the housework, and she plans to send Mattie packing. Ethan is crushed. But Zeena is adamant, and her decision is final. That night, Ethan kisses Mattie for the first time.
The next day, Ethan takes Mattie to the train station. They take a long ride and do some walking together, and both confess their love for one another. They decide to go sledding, something they had planned on but had never gotten around to. The first ride down the hill is exhilarating. On the way back up, both break down into tears. Mattie asks Ethan to take them down on a second ride, but this time she wants him to steer them into the big elm tree at the bottom of the hill. She wants to die with him.
Ethan does as she asks. But the suicide attempt is unsuccessful. Both of them live.
We move to twenty-four years later, with the narrator entering the Frome's home. In the kitchen there are two women: one tall and severe, and the other shriveled and paralyzed. The paralyzed woman is foul and hateful: Ethan introduces her as Miss Mattie Silver.
We finish with the narrator talking to Mrs. Hale, the old widow with whom he lodges. Mrs. Hale tells him that after the accident, Mattie had nowhere to go. The Fromes took her in. Zeena, once so sickly, somehow has found the strength to take care of all of them. Not many people go to the Frome farm anymore; Mrs. Hale is an old friend of theirs, and she visits once or twice a year, but she always finds the experience painful. She cannot bear the expression of suffering on Ethan's face. Mrs. Hale confides in the narrator that she thinks it would have been better if Mattie Silver had died. Ethan, Mattie, and Zeena are three ruined and bitter people, doomed to spend the rest of their lives under the same roof.