The Narrator, an engineer assigned to a job at a power plant near the town of Starkfield, MA, is intrigued by a tall crippled man he sees at the local post office. He learns that the man, Ethan Frome, was injured in a sledding accident 24 years earlier, but can get little more from the secretive locals. Circumstances lead the narrator to hire Ethan to drive him to and from his work. One night a violent winter storm forces Ethan to invite the Narrator to stay overnight at the Frome farm, where what he sees inspires him to reconstruct the tragedy.
The Narrator's vision begins with 28-year-old Ethan Frome peering through a church window at 21-year-old Mattie Silver, Ethan's wife's cousin. Mattie works at the Frome farm, where she provides domestic help to Zeena, Ethan's ailing wife, in return for room and board. As Ethan watches, Mattie dances with the arrogant Denis Eady, son of the town's wealthy grocer. Jealous, Ethan eavesdrops as Mattie refuses Denis's offer of a ride home and begins the two-mile walk back to the farm alone. Ethan hurries after her and they continue past a dangerous sledding hill, where Mattie's friend Ruth Varnum and Ruth's fiancé Ned Hale have recently avoided a serious accident. The attraction between Mattie and Ethan is palpable, but unspoken. When they reach the farm, they are surprised to find the door locked. Zeena greets them at the door, complaining that she is feeling "too mean to sleep." Ethan goes to bed with an uneasy feeling that Zeena guesses his feelings for Mattie, though she gives no outward sign.
The next day, Ethan postpones hauling a delivery of lumber to Andrew Hale, a local builder. Stopping at the farmhouse, Zeena, dressed in traveling clothes, informs him that she is making an overnight trip to Bettsbridge to consult a promising new doctor about her "shooting pains." Ethan quickly agrees to the plan, realizing that it will allow him to be alone at the farm with Mattie. He lies to Zeena that he can't take her to the station because he must collect payment from Andrew Hale.
Although he knows Hale never pays in advance, Ethan goes to him for the money in order to avoid being exposed as a liar. But Hale politely declines his request, and Ethan does not press him. Returning empty-handed to the farm, he finds Mattie presiding over a carefully-laid supper table. The blissful scene is shattered, however, when Zeena's red pickle-dish, a favorite wedding present, is knocked to the floor by the cat. Anticipating Zeena's anger, Mattie is terrified, but Ethan assures her that he will glue the fragments together before Zeena returns. The two go upstairs to bed without declaring their passion for one another or so much as touching.
The next day, farm work and bad weather conditions delay his errand to buy glue to mend the pickle-dish. When he returns home, he learns from Mattie that Zeena has already arrived and gone straight up to their room. Collecting himself, Ethan goes up to greet her, only to learn that the doctor has told her she will die unless she hires more efficient domestic help. She tells him a new hired girl will arrive the following day, and that Mattie must go immediately.
Mattie, waiting at the supper table, learns of her dismissal from Ethan, who kisses her passionately, no longer able to hide his feelings. Zeena approaches and interrupts them. She joins them at the dinner table, although previously she had claimed to be too ill to eat. Complaining of heartburn, Zeena leaves the table in search of stomach powders, but returns carrying the broken pickle-dish. Mattie confesses, which only fuels Zeena's determination to replace Mattie.
That night, Ethan starts to write a letter informing Zeena he has decided to elope with Mattie and go out West. Considering the plan further, though, Ethan realizes that he has no way of getting even the bit of money needed to travel West. He's also afraid of what will become of Zeena if she can't sell the farm. He falls asleep, leaving the letter unfinished.
Ethan decides to approach Hale and lie in order to get the money he needs. But at Hale's house he meets Hale's wife, who praises his dedication to Zeena. Her compassion makes Ethan ashamed of his plan to lie, and he gives it up. He returns to the farm to find Mattie's departure already underway. He tells Zeena that he, not the farmhand Jotham Powell, will drive Mattie to the train.
Instead of driving directly to the train station, Ethan and Mattie first go to Shadow Pond, the site where they had first fallen in love. Afterwards, they stop at the sledding hill and Ethan proposes that they go for the ride they've often considered taking. The first ride is accomplished without incident, but then Mattie suggests that they go down again, but steer into a big elm tree at the bottom of the hill rather than face parting from one another. Ethan complies—but just before they strike the tree Ethan sees a vision of Zeena's face, and momentarily swerves. Neither of the two are killed by the collision, but both are crippled for life.
The frame story resumes 24 years later, as the Narrator follows Ethan into the farmhouse kitchen. There he encounters two gray-haired women, one tall and thin, the other huddled in a chair. The tall one is Zeena, and the paralyzed woman, whose voice whines just like Zeena's, is Mattie Silver.
The following day, the Narrator tells his landlady, Mrs. Ned Hale, about his night at the Frome farm. The Narrator and Mrs. Hale talk sympathetically about Ethan. They describe him as imprisoned on the poverty-stricken farm with two discontented hags, doomed to contemplate the ruin of his hopes and to blame himself for his role in their destruction.