Edith Wharton wrote Ethan Frome as a frame story — meaning that the prologue and epilogue constitute a "frame" around the main story. The "frame" is The Narrator's vision of the tragedy that befalls Ethan Frome. The frame story takes place nearly twenty years after the events of the main story and is written in first person, revealing the thoughts and feelings of The Narrator. The main story, which describes the three and a half days before and including Ethan and Mattie's sledding accident, is written in third person — an omniscient narration that allows Wharton to relate the thoughts and feelings of all the characters.
Ethan Frome begins when The Narrator, an engineer who is living temporarily in Starkfield, Massachusetts while working on a project in a nearby town, becomes curious about Ethan Frome. The Narrator questions his landlady, Mrs. Ned Hale, and Harmon Gow, a long-time resident and former stagecoach driver, about Ethan. They provide The Narrator with bits and pieces of information about Ethan, which make him even more intrigued with the story of Ethan's life.
Temporarily unable to get to and from the train station in Corbury Flats, The Narrator acts on Gow's suggestion and asks Ethan to transport him back and forth. After a week of riding with Ethan, The Narrator and Ethan are caught in a blinding snowstorm on their return to Starkfield. Ethan invites The Narrator to spend the night at his farmhouse. During his unexpected stay with Ethan, The Narrator is able to glean information about Ethan's life.
As a young man, Ethan Frome wanted to become an engineer. He left home, attended a technological college in Worcester, Massachusetts, and spent time in Florida actually working on a small engineering job. His dream was to settle in a metropolitan area where he could take advantage of the opportunities city life offered. Unfortunately, Ethan's studies (as well as his dreams) come to an abrupt halt when his father died and his mother became ill soon afterwards. He returned to Starkfield, Massachusetts to care for his mother and to run the family farm and sawmill. Realizing that he couldn't do everything by himself, he made arrangements for his cousin Zenobia (Zeena) Pierce to live with them. Zeena took over the care of Ethan's mother as well as the household duties. After his mother's death, Ethan couldn't imagine being alone again on the farm, so he married Zeena.
In an attempt to reclaim his dreams and move to a metropolitan area, Ethan tried to sell the farm, but his efforts were unsuccessful. After a year of marriage, Zeena became well known to the people in Starkfield for her "sickliness." She suffered from a myriad of illnesses and her disposition became irritable and disagreeable. Ethan's dreams were doomed.
As the main story begins, Mattie Silver, a cousin of Zeena's whose parents' deaths left her destitute, has been a part of the Frome household for a year. Although Mattie is grateful to have a roof over her head and work as an aide to her cousin, she is, however, quite forgetful and often spends time dreaming rather than working. As a result, Ethan, who has secretly fallen in love with Mattie, completes many of her chores.
Three days before the "smash-up," Ethan goes one evening to meet Mattie, who is socializing at a church dance, and walk her home. He feels jealous when he observes Denis Eady, a local grocer and proprietor of the livery stable, flirting and dancing with Mattie. After Mattie refuses a ride home with Eady, she and Ethan walk home arm-in-arm.
The next day, Zeena tells Ethan that she's going to Bettsbridge to see Doctor Buck and spending the night with her Aunt Martha Pierce. Zeena asks Ethan to drive her to the train station, but Ethan tells her that he can't because he's going to see Andrew Hale, owner of a construction company in Starkfield, to get paid for lumber he sold him. He suggests that Jotham Powell, a man who helps out around the Frome farm, drive her to the train station. Because Ethan had no intention of seeing Hale, he absolves his guilt about lying to Zeena by actually going to see Hale and asking for an advance on his load of lumber. As Ethan expects, Hale declines to pay him then.
That evening, Mattie makes a particularly nice supper for Ethan. She even uses one of Zeena's best dishes, made of red glass, which is stored on the top shelf in the china closet. During the dinner, the cat knocks Zeena's red dish off the table and it breaks on the floor. Ethan pieces the dish together, puts it back on the shelf in the china closet, and promises to glue it together before Zeena returns home. The rest of the evening Ethan and Mattie spend the evening conversing with each other, well content in each other's company.
The following day, Ethan rushes through his work, then home to glue the red dish together before Zeena returns home. To his surprise, when he gets home with the glue, Zeena is already there. Zeena informs Ethan that she has "complications" and will need a "hired girl." Zeena tells Ethan that she hired a girl when she was in Bettsbridge who will be arriving on the train the next afternoon and that Mattie will have to leave so the new girl can have Mattie's bedroom. Ethan is angry, but realizes that Zeena will have her way. He tells Mattie that she will have to leave and he kisses her for the first time. Zeena comes into the kitchen furious because she has found her broken red pickle dish.
Ethan wants to go away with Mattie, but can't leave Zeena destitute. He understands that he is Zeena's prisoner. In the morning, Ethan again goes to visit Mr. Hale to ask for advance payment on lumber, and on his way, stops to speak to Mrs. Hale, who empathizes with him. He realizes that he can't take advantage of the Hales' understanding and returns home. Daniel Byrne, a neighbor, takes Mattie's trunk to the train station. Ethan insists that he will take Mattie to the train station himself.
On the way to the train station, Ethan takes Mattie to Shadow Pond where they first fell in love with each other. At the top of School House Hill, they find a sled and go sledding, successfully swerving, just missing the elm tree at the bottom of the hill. Before taking the sled down the hill again, Mattie tells Ethan that she would sooner die than to live without him. They agree that death would be better than living apart. With the intention of committing suicide, Mattie and Ethan head straight for the elm tree at the bottom of the hill. The suicide attempt fails. Mattie is taken to Mrs. Ned Hale's house to be cared for after the "smash-up" and Ethan is taken to the minister's house. Ethan and Mattie are taken to the Frome farmhouse when they are physically able and are cared for by Zeena. Despite injuries from the smash-up, including a permanent limp, Ethan manages to support the three of them by resuming working on the farm and in the sawmill.
When The Narrator stays overnight at the Frome farm, over twenty years after the smash-up, he is surprised to find that Mattie — crippled by the accident — complains incessantly. In fact, because the women are now so much alike, he has difficulty distinguishing them.