The basic situational analysis lays in the irony of the situation itself.
The author brings us to the present time, when the complete story is revealed to us. At first, we found out that Ethan had been living in a deadful state of oppression and lack of love in his marriage to Zeena. We also know that the only glimmer of hope he saw in living life for a purpose was the presence of Mattie, whom he fell in love with.
After many obstacles, Ethan manages to spend one night having dinner with Mattie until the red pickle dish falls, exposing that Ethan had the nerve to go against Zeena's wishes and take out her much valued dish just for the sake of dining with Mattie.
After Zeena discovers the deed and she asks Mattie to leave the home, Ethan and Mattie realized the pity of their lives and decide for a suicide pact to end their misery and be together forever in eternity.
Well, here comes the irony- They did not die. Instead, they were extremely messed up from the accident and both became crippled.
Now they are even more oppressed not only in the inside but on the outside. Just as in the beginning of the story, there are the same characters in the same scenario, but the roles have changed.
Now, Zeena is taking care of the would-have-been mistress of her husband who now turned into a whiny and annoying baggage around the house. Zeena is now the ruler supreme, in more control than ever, especially after reasserting her power over Ethan and Matty, who once tried to escape from HER.
Finally, there is poor, miserable Ethan Frome even more poor and more miserable than ever, now having to deal with TWO problems, instead of one. And, in addition to that, he has to live with himself.
In a way we can say the ending was not expected, as the situation for Ethan could have not been worse. But it did.
In the words of Mrs. Hale,
“I don’t see’s there’s much difference between the Fromes up at the farm and the Fromes down in the graveyard; ’cept that down there they’re all quiet, and the women have got to hold their tongues.”