There are certainly quite a few tricky expressions in O. Henry's “Between Rounds” that might trip up readers. Let's look at some of these to clarify them.

We'll begin with the first paragraph that sets the scene for the story. It is a bright May night, and spring is flourishing. The parks are green and busy with people trying to sell their merchandise. Summer-resort agents are also busy, trying to convince people to accept their deals. Many people are in a mild mood, not answering each other sharply but rather enjoying the entertainment of music and games.

That is not true of Mr. and Mrs. McCaskey, though. Mr. McCaskey is late again, and Mrs. McCaskey is getting hotter—i.e., angrier—as her supper cools. Mr. McCaskey finally comes up the steps, carefully avoiding stepping on his neighbors. The “size 9, width Ds” remark refers to the size of his shoes. He is being careful where he sets his feet.

The McCaskeys speak in a delightful dialect that may, however, need a bit of translation. Mrs. McCaskey throws words at her husband instead of kitchenware at first, saying that he will apologize to people he accidentally steps on in the street, but he will walk all over his wife with no remorse at all. She has been looking out the window (“windy”) for quite some time now. Supper is cold and wasted, and they don't have that much money to start with since he has the habit of drinking up his wages at the local bar on Saturday night. Mrs. McCaskey can't even pay the gas man.

Mr. McCaskey replies that his wife's scolding is insulting, or ruining, his appetite for his food. He tells her that politeness is the foundation of society but then proceed to order her to get her “pig's face” out of the window and see about supper. Needless to say, this does not go over well, and the couple begins to throw things at each other.

Quite a food fight follows as the McCaskeys throw everything from cheese to coffee to roast pork to a wash basin at each other. They seem to actually enjoy themselves immensely, but they are interrupted by a scream from downstairs. The landlady Mrs. Murphy has lost her little boy, Mike, and the boarders hurry off to hunt for him or at least lament his possible fate. All the boarders are affected by this news, even the two unmarried sisters (the “old maids, Misses Walsh”). Major Griggs sees his opportunity to go have a drink (a “rye-high”) at the pub while he is asking after Mike.

Finally, the boy is discovered curled up in a role of linoleum flooring under the bed, and the boarders settle back down. The McCaskeys happily resume their fight, now arguing about whether or not their hypothetical child would have done such a thing.