In Ethan Frome, what is the significant realization that Ethan makes?
When Zeena declares that Mattie will have to leave, Ethan is thrown into an emotional turmoil at the thought of living without her. The night before her departure, Ethan goes to his study and agonizes over sending Mattie away. The idea occurs to him that he could go with her and that Zeena would not realize he was gone until after he had made his escape. He begins a letter to Zeena to leave behind. He then finds an old copy of the newspaper with an advertisement about "reduced fares" for those going to the West.
Reality crashes down upon Ethan. He cannot leave Zeena destitute, but if he leaves her the farm, he will have no money to support himself and Mattie in a new life. He also knows that Zeena could not possibly keep the farm going by herself. Furthermore, after reading the advertisement in the paper, he finds he doesn't have enough money even to pay their fare to go west. He cannot borrow money; he has nothing to offer as security for a loan, and no one in Starkfield would give him an unsecured loan. Ethan realizes then that there is no way out for him. He is "a prisoner for life, and now [with Mattie's leaving] his one ray of light was to be extinguished." This truth leads to Ethan and Mattie's suicide attempt the next day.