On the way home from school, a distracted Mary is barely listening to Laura. The two girls are picked up by their father who is on his way home, as well.
He hands Mary a letter from her fiance, John Sanderson, who is attending college in Chicago. Mary keeps much of the letter to herself, telling Laura at home some of what he wrote. He writes of the excitement of the city and of the life he now leads, his love for her and a cotillion that will be held the next week.
Mary is depressed, being so far away from him and wishing she could attend the dance with him. In the meantime, Charles has an announcement. He has been asked to represent their district at the Grange convention - an organization devoted to farmers - in Chicago. The trip is completely paid, too.
Mary is excited that she will be able to send John's Christmas present, which she had not been able to give him when he didn't return home for the holidays, with her parents. She begins thinking of all the things she can have them ask him.
Caroline privately discusses her feeling with Charles that Mary should go with him instead of her. She remembers being a young girl in love.
She shows Mary the dress she wore to a Spring dance many years before and recalls how she fell in love with Charles that night when he complimented her beauty and gave her cornflowers to put in her hair. She offers to alter the dress for Mary so she can wear it to the cotillion in Chicago.
During the train ride, Charles and Mary are surprised when they are served a fancy, private lunch. When they arrive at their hotel, they find their room has already been reserved for them and are escorted to a fancy suite with private bedrooms and a bath.
But Mary is most eager to see John. Charles takes her down to the newspaper where John works and he spots them across a street. He runs to her and they embrace warmly. John's employer, Mr. Fletcher Hancock, approaches him, but is delighted to meet Mary and her father.
He offers to take Charles to the convention as he is headed that way anyway and invites them all to dinner that evening. John and Mary are left alone and she gives him his Christmas present - a plaid shirt she made herself.
They stroll throughout Chicago and John shares the scenery and novelties, such as chewing gum, with her. He is forced to leave when a school-mate of his named Wesley arrives and reminds him of an appointment he has with a professor.
It turns out that the professor is a young woman with whom John is having a relationship. She criticizes his shirt and reminds him of their plans to attend the cotillion.
In the meantime, Charles has aquainted himself with a man named O'Connell at the convention and has mentioned his desire to have a grain elevator established closer to Walnut Grove where the farmers from there and the surrounding towns will be able to take their crops. He is later delighted to find that O'Connell has talked up the idea with some important men who are prepared to follow through on it. He is disappointed to learn, however, that he is expected to return the indulgence by voting against a state measure to regulate the railroad industry - a measure he personally favors.
Later that evening, he is disturbed when a woman of obviously ill-repute appears at his hotel door explaining that she had been ordered by Stanley Hollingsworth - a prominent figure in the railroad business. Charles explains that there has been a mistake, but realizes that the amenities that he's been enjoying have all likely been paid for by the same Stanley Hollingsworth.
Charles is further disgusted the next day by the shenanagins at the convention with back-door dealings, gambling, women and other vices. He confronts Hancock whose paper published a rose-colored version of events. Hancock explains that the paper has a responsibility to protect its readers from certain unsavory details for the greater good that the Grange provides. Charles believes that the most important detail in publishing papers is the truth. Hancock is finally forced to admit that the advertising paid for by the railroad keeps his paper in business.
That evening, Charles drops Mary off at the cotillion before going to the vote. John asks if her father can escort Mary home that evening after the dance as he must cover the event for the paper.
In fact, this is a ruse to attend the dance with both Mary and his girlfriend. He excuses himself regularly on newspaper business to meet each girl, until the young woman storms off when she finds she is not a priority.
At the convention, O'Connell gives a stirring speech over valuing the railroad as an ally - which understands the farming community - over bureaucrats in Washington who are too far removed from them to truly appreciate their needs.
A disgruntled Charles demands to know how much he was paid to say that. He delivers a fiery condemnation of the corruption he has witnessed and how he may not be wealthy or well-educated, but he plans to vote for the measure.
His mood is still sour as he returns to the dance. John's respite has not lasted as his girlfriend returns and forgives him. When Charles spots John bringing drinks out to a balcony, he follows and is shocked to see John kissing this strange young woman passionately.
The awkward moment is broken and the two men are left alone. Charles asks John if he still loves Mary. Though John cares for her still, he is forced to admit that he has grown apart from her due to his time in the city and does not have the nerve to tell her to her face. Writing is his strength and he had planned to send her a letter after she left.
Charles tells him that he owes Mary the truth and to give her that respect by telling her personally.
That night, a devastated Mary does not think she will ever love again. Charles supports her by explaining that hurting helps people appreciate the happy times even more. He knows that, someday, she will meet someone else even though she doesn't believe it will ever happen. They both agree that Chicago is not suitable for them and it's time to go home.
On the train back, Charles muses that they are not likely to have a fancy lunch this time. The unhappy Mary is quiet as a boy close to her age sits across from her and offers her a sandwich. He introduces himself as Patrick. They begin to talk and she finds that he is moving to a town close to Walnut Grove that doesn't have a school, so he'll be attending hers.
Charles smiles wisely to himself as his daughter chats animatedly with Patrick as the train carries them home.