Howard comes into Andy's office in a whirlwind of energy. Things have been going so well between him and Millie that he's ready to propose. The only problem is, he doesn't know how to about doing it. Andy convinces him to propose to her right at the bakery where she works.
When Howard goes into the bakery, every time he's working up to the proposal, they get interrupted by patrons. Finally, Howard gets it out before anyone else can come in. Millie readily says yes, and the two of them go off to tell Andy and Helen, whom they ask to be their best man and maid of honor, respectively. The wedding's set to take place in one week in Millie's hometown of Wheeling.
On the train ride to West Virginia, Howard and Millie begin to discover some things about the other that they previously hadn't thought through. Howard's regulated, tight-fisted ways drive Millie crazy, and her carefree ways with time and money make him uneasy. The climax of their fight is when Millie asks Howard to shave his moustache for her, which he flat out refuses.
The next morning, with their fight not resolved, Millie and Howard continue to learn about their many differences. Howard is a morning person, and Millie is not, and by the time they get to Wheeling they still have not resolved their differences.
When the train reaches the platform in Wheeling, Millie and Howard practically race past her parents to steal away and talk privately for a few moments, leaving a sheepish Helen and Andy to make small talk with her family. When Millie and Howard return, they make the announcement that they're calling off the wedding. Not knowing what to do, Helen and Andy congratulate them.
On the train ride back, the four friends have a delightful time, and when Andy offers to pay for dinner, this time Howard doesn't refuse.